Webasto Thermo Top Pro 120 Instruction manual

Water Heater
Thermo Top Pro 120 | 150
English
Workshop Manual

Contents
2 9039412C Workshop manual TTP 120 _ 150
Contents
1 About this document .......................... 3
1.1 Purpose of the document .......................................... 3
1.2 Using this document.................................................. 3
1.3 Use of symbols and highlighting ................................ 3
2 Safety ................................................. 3
2.1 General safety information .......................................3
2.2 Qualification of personel............................................4
2.3 Working on the heater .............................................. 4
2.4 Working on the vehicle..............................................4
2.5 Heater test run .......................................................... 4
2.6 Checks ......................................................................4
3 Information regarding the heater ....... 5
3.1 Basis .......................................................................... 5
3.2 Special variants (Rail, CPoff, Chiller, ADR)...................5
4 Description of the components........... 6
4.1 Overview of the subassemblies ..................................6
4.2 Burner head............................................................... 8
4.3 Combustion air fan .................................................... 8
4.4 Drive motor ...............................................................8
4.5 Fuel pump with solenoid valve................................... 9
4.6 Nozzle block preheater .............................................. 9
4.7 Ignition spark generator with ignition electrodes .......9
4.8 Fuel nozzle and baffle plate ....................................... 9
4.9 Control unit ............................................................. 10
4.10 Flame monitor ......................................................... 10
4.11 Pressure equalization element.................................. 10
4.12 Heat exchanger ....................................................... 10
4.13 Combustion tube..................................................... 10
4.14 Coolant temperature sensors ................................... 11
4.15 Exhaust gas temperature sensor .............................. 11
4.16 Coolant pump .........................................................11
4.17 Coolant ................................................................... 12
4.18 Fuel filter ................................................................. 12
5 Functional description ...................... 13
5.1 Introduction ............................................................ 13
5.2 Control elements .....................................................13
5.3 Switch the heater on and off ...................................13
5.4 Using the heater in hazardous material vehicles (ADR)
............................................................................... 13
5.5 Functional sequence ................................................ 14
5.6 Fault switch-off ....................................................... 15
6 Malfunctions and troubleshooting.... 15
6.1 Basics ...................................................................... 15
6.2 Fault list on the control element .............................. 15
6.3 Cause of malfunctions in the heater and systems..... 16
6.4 Instructions for cancelling the fault lock-out ............ 16
6.5 Heater unlocking instructions ..................................17
6.6 Overview of faults and fault codes........................... 17
7 Function checks .................................24
7.1 Basics .......................................................................24
7.2 Check and set CO₂ in exhaust gas.............................24
7.3 Checking exhaust gas temperature sensor ................25
7.4 Checking control unit ...............................................25
7.5 Check combustion tube ............................................25
7.6 Check the blower fan wheel .....................................26
7.7 Checking baffle plate................................................26
7.8 Checking drive motor ...............................................26
7.9 Fuel pump and check solenoid valve.........................26
7.10 Checking heater cartridge.........................................27
7.11 Check coolant pump.................................................28
7.12 Checking coolant temperature sensors .....................28
7.13 Checking ignition electrode ......................................28
8 Repairing and replacing components
..........................................................29
8.1 Required tools ..........................................................29
8.2 Installation notes ......................................................29
8.3 Disconnecting control unit connections ....................30
8.4 Disconnect burner head............................................30
8.5 Install burner head....................................................30
8.6 Removing control unit ..............................................30
8.7 Electrical wiring in the burner head...........................31
8.8 Removing baffle plate...............................................31
8.9 Removing ignition electrodes....................................32
8.10 Removing fuel nozzle................................................32
8.11 Removing ignition spark generator ...........................33
8.12 Removing fuel pump ................................................33
8.13 Installing fuel pump..................................................33
8.14 Removing nozzle block preheater .............................34
8.15 Removing blower fan wheel .....................................34
8.16 Removing drive motor ..............................................35
8.17 Remove heat exchanger ...........................................35
8.18 Remove combustion tube .........................................35
8.19 Remove coolant temperature sensors .......................36
8.20 Install coolant temperature sensors...........................36
8.21 Removing exhaust gas temperature sensor ...............36
8.22 Installing exhaust gas temperature sensor.................37
9 Packaging / storage / shipping ..........37
9.1 General information .................................................37
9.2 Ideal position............................................................37
9.3 Storage and transportation.......................................38
10 Electrical incorporation......................38
10.1 Information on the electrical connection...................38
10.2 The heater in hazardous material vehicles (ADR) .......38
10.3 Legend and remarks regarding wiring diagrams........38
10.4 Cable colours / cable cross-sections .........................39
10.5 Connector and pins ..................................................39
10.6 Wiring diagrams ......................................................40
11 Technical data ...................................48
12 List of abbreviations ..........................48

About this document | 1
9039412C Workshop manual TTP 120 _ 150 3 / 49
1 About this document
1.1 Purpose of the document
This workshop manual is designed to assist trained personnel
with maintenance of the Thermo Top Pro 120 | 150.
The document is part of the product and contains all the in-
formation, settings and instructions necessary to maintain the
product.
1.2 Using this document
lRead and understand this workshop manual before repair-
ing the product.
lRead and observe important safety instructions.
lRead and observe Operating instructions.
lRead and observe Installation instructions.
1.3 Use of symbols and highlighting
DANGER
This signal word denotes a hazard with a high degree
of risk which, if not avoided, may lead to death or seri-
ous injury.
WARNING
This signal word denotes a hazard with a moderate de-
gree of risk which, if not avoided, may lead to minor or
moderate injury.
CAUTION
This signal word denotes a hazard with a low degree of
risk which, if not avoided, will lead to minor or moder-
ate injury.
NOTE
This signal word denotes a Special Technical Feature or
(if not observed) potential damage to the product.
Refers to separate documents which are enclosed or
can be requested from Webasto.
üRequirements for the following necessary action
uNecessary action
2 Safety
The general accident prevention regulations and valid opera-
tional safety instructions must be observed. "General safety re-
quirements" that extend beyond the framework of these regula-
tions are specified in the following. The special safety require-
ments that pertain to this workshop manual are highlighted in
the individual chapters and procedural descriptions.
2.1 General safety information
DANGER
Danger of poisoning and suffocation
Do not operate the heater in closed rooms that do not
have an exhaust extraction unit.
uDo not switch on or operate the heater.
DANGER
Danger of scalding from leaking hot coolant
Scalding on opening the coolant circuit. The vehicle
coolant circuit is pressurised.
uAllow the engine to cool before working on the
vehicle coolant system.
DANGER
Hazardous material vehicles (ADR) must not be
switched on or off using a timer control or remote con-
trol.
CAUTION
Overheating possible
A battery disconnector (emergency off switch) may only
be actuated in the event of danger since the heater will
be switched off without after-running period.
CAUTION
Overheating
Insufficient bleeding can lead to a malfunction resulting
from overheating in heating mode.
Take care when bleeding the coolant system.
Always bleed:
- Before first commissioning the heater
- After replacing the coolant
NOTE
Correct bleeding can be identified by the fact that the
coolant pump is making very little noise.
NOTE
Incorrect handling
uProtect the heater against mechanical stress (e.g.
dropping, impacts or knocks).
uDo not stand on the heater.
uDo not place any objects on top of the heater.
uAvoid shutting down the heater incorrectly during
the after-running period. After switching off via the
control element, the fan of the heater continues to
run.
uAlways switch off the heater via the control ele-
ment.
uDo not disconnect from the power supply until the
after-running period has elapsed.

2 | Safety
4 / 49 9039412C Workshop manual TTP 120 _ 150
2.2 Qualification of personel
The personnel must have the following qualifications:
– Successful completion of Webasto training
– Corresponding qualification for working on technical
systems
– Read and observe installation, operating and important
safety instructions
2.3 Working on the heater
NOTE
Before dismantling the heater, disconnect the heater
power supply from the vehicle battery or remove fuses
F1 and F3.
NOTE
Always carry out a visual inspection before starting re-
pair work:
- Check the coolant system and fuel system for leaks.
- Check the combustion air and exhaust pipe for dam-
age and ensure they are clear.
NOTE
- Collect the coolant running out of the system in a suit-
able container.
- Block or disconnect coolant hoses.
- Dispose of coolants in an environmentally friendly
way.
The main battery power must not be disconnected as long as
the heater is operating or after running due the risk of the
heater overheating and consequently the overheating safeguard
tripping.
Once the heater and all coolant-carrying components have been
installed, fill the entire coolant system according to the vehicle
manufacturer's specifications.
Bleed the system according to the vehicle manufacturer's spe-
cifications and check for leaks with the default system pressure
of the vehicle.
NOTE
Replace component:
Within the warranty period, send in only the defective
component (not the entire heater) to Webasto.
NOTE
When on-board power supply is applied, never discon-
nect the connector from the heater.
2.4 Working on the vehicle
NOTE
The heater temperature must not exceed 120 C when
switched off. See Technical data.
2.5 Heater test run
NOTE
Even if you use the timer, the heater must not be oper-
ated in enclosed spaces such as garages and workshops
without an emissions extraction system.
2.6 Checks
Webasto recommends to carry out the following servicing jobs
before and after each heating period:
1. Read out the fault code memory.
2. Clean heater exterior (make sure no water gets in).
3. Check the electrical connections for contact corrosion and
firm seating.
4. Check exhaust gas and combustion air line for damage and
ensure that they are clear.
5. Check the fuel line and filters for leaks.
6. Check the coolant circuit and coolant pump.
7. Check hoses for cracks.
8. If fitted and necessary, change the fuel filter.
9. Commission the heater.

Information regarding the heater | 3
9039412C Workshop manual TTP 120 _ 150 5 / 49
3 Information regarding the
heater
3.1 Basis
The Thermo Top Pro 120 | 150 heaters consist essentially of the
following main components:
lBurner head (with fan, fuel pump, control unit)
lCombustion chamber
lHeat exchanger
A coolant pump (type U4850) is installed in the vehicle near the
heater and guarantees the required heat transport via the
coolant circuit.
A B C D
F
E
G
H
I
J
K
Q
P O N M L
Fig.1 Overview of heater and connections
A Spray guard (optional) J Exhaust gas outlet
B Burner head K Original vehicle coolant hose
(inlet)
C Electrical Connections L Fuel line
D Coolant outlet of heater M Fuel hose clamp
E Coolant temperature
sensors with cover
N Fuel connector
F Heat exchanger O Seal
G Coolant inlet of heater P Screw for fuel connector
H Coolant hose (inlet) Q Dummy connector for
coolant pump (for CPoff
variant)
I Exhaust gas temperature
sensor
NOTE
This workshop manual describes the retrofit version of
the heater. In the case of heaters installed directly by
the vehicle manufacturer, different control units with
different connectors and different software as well as
different application parts may be used which are not
described in this manual. For these heaters, information
is only available in the documentation of the vehicle
manufacturer.
3.2 Special variants (Rail, CPoff, Chiller,
ADR)
3.2.1 Thermo Top Pro 150 Rail
This is a heater model for installation and operation in rail
vehicles. The essential functions correspond to the standard ver-
sion of the heater.
3.2.2 Thermo Top Pro 120 | 150 CPoff
In the case of the "CPoff" variant, controlling and monitoring
the coolant pump is deactivated by the heater. Corresponding
implementation of a coolant pump must be ensured in the
vehicle by the customer. For information regarding pump selec-
tion and design, see chapter4.16, "Coolant pump" on page
11. Connection X1 on the control unit, which is provided for
the coolant pump, does not have a function in this variant and
must be closed in this variant with a dummy connector for seal-
ing purposes (see Fig. 1, position Q).
WARNING
Use of an unsuitable pump or malfunction thereof may
result in the heater being damaged. Compared to the
basic variant, there is no monitoring of the pump as
well as a control unit via the heater is not possible in
heating mode. This must be ensured by the customer as
part of the vehicle application.
The additional functions correspond to the standard version of
the heater.
3.2.3 Thermo Top Pro 120 Chiller
This variant is based on the previous "CPoff" and has the same
requirements for use of the coolant pump. However, operation
is only permitted in the "Motor on" configuration. As a result,
the permissible coolant temperature is limited to 65°C. The
heater must be connected according to the chiller-specific wir-
ing diagram (see Fig. 56).
3.2.4 Thermo Top Pro 120 | 150 ADR
In this case it is the standard version of the heater with ADR-
specific provision in the application. Special requirements for in-
stalling and operating the heater in accordance with the spe-
cifications of the European Agreement concerning the Interna-
tional Carriage of Dangerous Goods by Road (ADR), can be
found in the general installation and operating instructions. Re-
garding ADR, see also: https://www.unece.org/trans/danger/
publi/adr/adr_e.html

4 | Description of the components
6 / 49 9039412C Workshop manual TTP 120 _ 150
4 Description of the components
4.1 Overview of the subassemblies
AG
AH
A I
AJ
AF
AE
AD
AD
AD
AC
AB
AA
AA AA
YZXWV
U
T
S
R
Q
P2
P1
P
O
N
M
L
K
J
I
HG
F
E
D
CB
A
Fig.2 Exploded view
The following legend extends over this and the next page.
A Ignition spark generator S Coolant temperature sensors
B Screw for ignition spark generator
M5x14 PH2 (on fuel pump) (2+/-0.2Nm)
T Cover for sensors
C Ignition electrodes U Collar screw on cover for sensors
M4 T20 (2+/-0.2Nm)
D Cylinderbolt for ignition electrodes
M4x12 SW3 (on ignition spark generator) (3+/- 0.3 Nm)
V Exhaust gas temperature sensor
E Burner head W Spring clip
F Screw for drive motor
M3x10 T10 (on burner head) (2+/-0.2Nm)
X Screw for spring clip
M4x5.5 T20 (2+/-0.2Nm)

Description of the components | 4
9039412C Workshop manual TTP 120 _ 150 7 / 49
G O-ring fuel pump (small) Y Burner
H Fuel pump with solenoid valve Z Seal
I Screw for fuel pump
M5x45 T25 (on burner head) (3.5+/-0.35Nm)
AA Nut
M8 SW13 (burner head on heat exchanger) (19+/-
2Nm)
J Fuel nozzle
SW16 (20+/-2Nm)
AB Cable tie for electrical cables (nozzle block preheater
and ignition spark generator)
K Baffle plate AC Clip for electrical cables (on burner head)
L Clip for nozzle block preheater AD Screw for fan cover
40x14 T20 (3 +/- 0.3 Nm)
M Screen (fuel pump) AE Combustion air spray guard (optional)
N O-ring fuel pump (large) AF Fan cover
O Heater cartridge, nozzle block preheater AG Circlip for blower fan wheel
DIN471 6x0.7 (on drive motor axle)
P Control unit (P1 pressure equalisation element, P2 optical
sensor)
AH Blower fan wheel
Q Screw for control unit
4x14 T20 (on burner head) (3+/-0.3Nm)
AI Drive motor
R Heat exchanger AJ Axle connection

4 | Description of the components
8 / 49 9039412C Workshop manual TTP 120 _ 150
4.2 Burner head
AB
Fig.3 Burner head
A Burner head B Control unit
ABCD
E
Fig.4 Burner head details
A Fan with cover
D
Housing
B Drive motor E Fuel pump with solenoid valve, ig-
nition spark generator, ignition
electrodes, nozzle with pre-heat-
ing and baffle plate.
C Axle connection
The burner head can be removed for repair and maintenance
purposes.
4.3 Combustion air fan
BA C
Fig.5 Combustion air fan
A Spray guard (optional) C Fan wheel
B Fan cover
The fan wheel delivers the air required for combustion in the
combustion tube via the combustion air inlet. The air is sucked
in through the air intake opening in the fan cover.
Optionally, a spray guard or a combustion air intake line ap-
proved by Webasto can be attached to the fan cover.
4.4 Drive motor
B
A
Fig.6 Drive motor
A Axle connection B Drive motor
The drive motor drives the fan wheel and the fuel pump using a
axle connection (shaft coupling).

Description of the components | 4
9039412C Workshop manual TTP 120 _ 150 9 / 49
4.5 Fuel pump with solenoid valve
D
B
A
C
Fig.7 Fuel pump with solenoid valve
A Solenoid valve C Fuel pump
B Fuel nozzle
D
Axle connection to the drive motor
The fuel for combustion is supplied by the fuel pump. The fuel
pump is driven by the drive motor using an axle connection to
the drive motor (shaft coupling).
The fuel pressure is increased to approx. 11 bar in the fuel
pump. The solenoid valve integrated into the fuel pump opens
or closes the fuel supply to the fuel nozzle as a function of the
heating mode.
4.6 Nozzle block preheater
D
B
A
C
E
Fig.8 Nozzle block preheater
A Fuel nozzle D Heater cartridge
B Nozzle block E Fuel pump
C Fastening clamp
The nozzle block preheater consists of a heater cartridge
(130W) and is part of the standard equipment of the heater.
At low temperatures (factory setting: T < 5 °C, depending on
the application of the heater), the heater cartridge warms the
nozzle block and the fuel nozzle. This ensures an optimised
atomisation of the fuel.
The heater cartridge is activated automatically by the control
unit.
4.7 Ignition spark generator with
ignition electrodes
B
A
Fig.9 Ignition spark generator
A Ignition electrodes B Ignition spark generator
The high voltage for igniting the air-fuel mixture is generated in
the ignition spark generator. Ignition occurs by a high-voltage
spark crossing between the two ignition electrodes.
4.8 Fuel nozzle and baffle plate
B
A
C
Fig.10 Fuel nozzle and baffle plate
A Baffle plate C Fuel nozzle
B Ignition electrodes
The baffle plate guarantees the correct air distribution for the
combustion process.
The baffle plate is permeable to flame light and makes visual
flame monitoring possible with the control unit.

4 | Description of the components
10 / 49 9039412C Workshop manual TTP 120 _ 150
4.9 Control unit
NOTE
The control unit must not be disassembled.
EDBA C F
J
I
H
G
Fig.11 Inside and outside of control unit
A Pressure equalization ele-
ment
F Drive motor
B Flame monitor G Control element(s), vehicle
connection
C Ignition spark generator H Temperature sensors
D Nozzle block preheater I Heater power supply
E Fuel pump J Connecting coolant pump
The control unit controls the functional sequence and monitors
the heating mode. Sensors for continuously determining the
temperature and pressure are integrated into the control unit.
4.10 Flame monitor
An optical flame monitor in the control unit detects the flame
formation.
4.11 Pressure equalization element
A pressure equalisation element prevents the humidity from
penetrating the inside of the control unit and establishes an
equalisation of pressure with the surrounding area (altitude
compensation).
4.12 Heat exchanger
Fig.12 Heat exchanger
The heat exchanger transfers the heat generated in the combus-
tion process to the coolant circuit.
Components associated with the heat exchanger include:
lSeal
lCoolant temperature sensors with cover
lExhaust gas temperature sensor
4.13 Combustion tube
Fig.13 Burner
The air-fuel mixture is burned in the combustion tube. The gen-
erated hot flue gases heat the coolant flowing through the heat
exchanger.

Description of the components | 4
9039412C Workshop manual TTP 120 _ 150 11 / 49
4.14 Coolant temperature sensors
B
A
C
Fig.14 Coolant temperature sensors
A Overheat sensor C Cover for sensors
B Coolant temperature sensor
The sensor values are used for the coolant temperature control
and for protecting the heater against overheating.
The sensors are connected to the control unit by the cabling.
4.15 Exhaust gas temperature sensor
B
A
Fig.15 Exhaust gas temperature sensor attachment and connector
A Exhaust gas temperature sensor
connector
B Exhaust gas temperature
sensor
A sensor is installed on the exhaust gas stub of the heater to
monitor the temperature in the exhaust gas. The sensor is con-
nected to the control unit by the cabling.
4.16 Coolant pump
The standard variant of the Thermo Top Pro 120 | 150 are oper-
ated with the coolant pump U4850. The coolant pump is
switched on by the heater control unit.
If using a CPoff heater variant (see chapter3.2.2, "Thermo Top
Pro 120 | 150 CPoff" on page 5), which can also be recognised
via the "CP OFF" label, then a coolant pump is controlled ex-
ternally. Exact specifications to this effect can be found at the
end of this chapter in the section "Use of an external coolant
pump".
B
A
C
Fig.16 Coolant pump U4850
A Coolant pump U4850 C Coolant inlet
B Coolant outlet
NOTE
The use of the U4850 coolant pump in military vehicles
or military applications is prohibited.
NOTE
The heater must be operated with a coolant pump.
Pumps that have been dropped must not be re-used.
Dropping may lead to external impact points and in-
ternal damage.
Possible cracks in the plastic part of the pump may lead
to a leakage in the pump compartment or the sur-
rounding area. This may result in operational failures of
the pump due to the ingress of coolant into the elec-
tronic area.
Characteristics of the coolant pump U4850
NOTE
Reactivation of the coolant pump motor:
The coolant pump motor can be reactivated from the
dry-running protection or sleep mode. This is done by
isolating the power supply for > for 2 min. After restor-
ing the power supply, the coolant pump motor starts in
soft-start again.
lStart-up
The coolant pump motor starts up within 2 seconds.
lProtection against blocking, running dry and overload
A continuous check of the coolant pump for blocking, run-
ning dry and overload is carried out during the start and
regular operation.
If such an error case is detected, the coolant pump sends a
corresponding diagnostic signal to the heater control unit
and automatically deactivates itself temporarily. The
coolant pump attempts to start again.
After 20 unsuccessful start attempts, the coolant pump
switches itself off. To carry out a renewed start attempt,
the coolant pump must be turned off and switched back on
again.
The coolant pump motor is not damaged by hydraulic over-
pressure of the coolant pump provided that the following
limits are observed:
– Max. overflow forwards: 2400 l/h
– Max. overflow backwards: 500 l/h

4 | Description of the components
12 / 49 9039412C Workshop manual TTP 120 _ 150
lOvervoltage protection
In the event of overvoltage, the coolant pump automatic-
ally shuts down at a voltage supply above 36 V (24 V) and
16 V (12 V). If the voltage drops to 35 V or 15 V, the pump
automatically switches itself on again.
If overvoltage is diagnosed, the coolant pump sends a cor-
responding diagnostic signal to the heater control unit.
lUndervoltage protection
BIn the event of undervoltage, the coolant pump automat-
ically shuts down at below 13.5 V (24 V) and 8 V (12 V)
power supply. If the voltage rises to 14.5 V or 9 V, the
pump automatically switches itself on again.
If undervoltage is diagnosed, the coolant pump sends a
corresponding diagnostic signal to the heater control unit.
lReverse-polarity protection
NOTE
The coolant pump motor is not equipped with internal
reverse-polarity protection.
lElectrical protection
NOTE
The fuse for the coolant pump must never be pulled out
during operation
The fuse for the coolant pump must never be replaced
when switched on.
lTransport and storage
The pumps should only be transported and stored in the
appropriate transport packaging. Unsorted transport (e.g.
bulk product) is not permitted.
NOTE
The coolant pump shuts off for:
- Overvoltage
- Undervoltage
- An internal fault
- Dropping below the minimum speed
- Permissible operating temperature exceeded
Use of an external coolant pump
The externally controlled coolant pump in the CPoff variant
must ensure that the coolant is delivered in the coolant circuit
of the heater or vehicle. It must satisfy the following technical
features:
Thermo Top
Pro 120
Thermo Top
Pro 150
Nominal volume flow [l/h]
(against 0.56 bar)
1500
Minimal volume flow [l\h]
(if lower than this then there
is a risk of overheating.
Heater may be damaged)
1100 1400
After-running period Min. 60 s
Connection piece diameter /
Reduction of cross-section
System diameter TTP120|150
=20mm.
Reduction of cross-sections
should be avoided.
The coolant pump must be in operation during the entire heat-
ing mode and during the after-running period.
4.17 Coolant
Follow the instructions of the vehicle manufacturer when check-
ing the coolant level.
NOTE
You will find further information in the installation in-
structions and at the vehicle manufacturer.
Coolant Mix ratio e.g. Glysantin®/water.
Permissible water/glycol (monoethylene glycol) mixes:
Glycol [%] Water [%]
Minimum 33 40
Maximum 60 67
4.18 Fuel filter
BA C
D
Fig.17 Fuel filter
A Fuel filter without heating C Electrical connection
B Fuel filter with heating
D
Bleed screw
The externally located fuel filter is used for separating sediment
from the fuel and therefore prevents blocking of the fuel nozzle.
Filter heating is available as an option. It is recommended or ne-
cessary to install filter heating under certain use and operating
conditions. See installation instructions.
The filter heating cut-in point is approx. -5 °C and the cut-out
point is approx. +5 °C.

Functional description | 5
9039412C Workshop manual TTP 120 _ 150 13 / 49
5 Functional description
5.1 Introduction
The Thermo Top Pro 120 | 150 is a water heater with coolant
temperature control, monitored by its integrated control unit.
To regulate the coolant temperature, the heater works in cycle
operation.
The necessary, continuous coolant flow is provided by a coolant
pump.
After the heater is activated, heating mode and the residual
heat utilisation/control pause are controlled automatically de-
pending on the switching thresholds.
Standard temperature range (standard
values)
Temperature
°C
Motor OFF 65 – 80
Motor ON 50 – 65
Residual heat utilisation, motor OFF 55 – 65
NOTE
The switching thresholds are dependent on the heater
variant and the type of heating mode.
To produce heat, the fuel is sprayed under pressure through a
fuel nozzle, mixed with combustion air and burned.
The volume of combustion air is provided by the fan.
The fuel is supplied by a fuel pump with pressure limiting valve.
The fuel pump is driven directly by the speed-controlled drive
motor and also has a temperature controlled nozzle block pre-
heater for improving fuel atomisation at low temperatures.
The fuel system is opened and closed by a solenoid valve at the
fuel pump.
The air-fuel mixture is ignited by a high voltage spark in the
combustion chamber.
Flame monitoring is done with a flame monitor (optical sensor)
in the control unit.
The coolant temperature and the exhaust gas temperature are
monitored by the sensor system in order to protect the heater
from overheating.
The correct volume of combustion air for combustion is main-
tained by the speed control of the drive motor. The speed con-
trol automatically compensates for the air pressure influence
(altitude compensation) on combustion.
The speed is calibrated for correct combustion in the Device
production department at Webasto. In case of service, calibra-
tion can be done in the workshop during CO₂ adjustment when
carrying out the Webasto-Thermo test diagnosis (WTT diagnosis
see chapter7.2, "Check and set CO₂ in exhaust gas" on page
24).
NOTE
If combustion does not take place, see chapter6, "Mal-
functions and troubleshooting" on page 15.
The operating state is displayed by the control panel or an indic-
ator lamp (LED).
5.2 Control elements
The Thermo Top Pro 120 | 150 heater can be controlled with
various control units such as a rocker switch, SmartControl/
Multi Control and ThermoCall TC4. A combination of control
elements is also possible in certain cases.
Observe the operating instructions for the control element.
5.3 Switch the heater on and off
The heater is switched on and off by different switch signals.
Depending on the system equipment, the switch signals are
produced by a switch, control element or a climate control sys-
tem.
DANGER
Overheating possible
An emergency off switch may only be actuated in the
event of danger since the heater will be switched off
without after-running period.
See the operating and installation instructions for the
control element.
If the documents are not available, these can be reques-
ted from Webasto.
NOTE
Always switch off the heater via the control ele-
ment
After switching off via the control element, the heater
switches to a short controlled run-on phase. Switching
off incorrectly, without after-run, can cause damage to
the heater.
5.4 Using the heater in hazardous
material vehicles (ADR)
It is not possible to set a preselection time in hazardous material
vehicles (ADR). The SmartControl (if present) shows how much
heater operation time is left (remaining operation time).
NOTE
An ADR after-running period is applied in the fol-
lowing cases:
- the generator signal (D+, light machine) is discontin-
ued.
- the pumping device (auxiliary drive) belonging to the
vehicle is put into operation.
After the end of the ADR after-running period, the
heater is in ADR locking mode.
NOTE
Release ADR lock:
uPut the pumping device belonging to the vehicle out
of operation.
uRestart the heater by switching it off and on again
using the control element.

5 | Functional description
14 / 49 9039412C Workshop manual TTP 120 _ 150
5.5 Functional sequence
Fig.18 Functional sequence
1 Switch on/ component test A Operating indicator
2 Supply B Coolant pump
3 External light request 1 C Fan
4 Pre-ignition/flame ignition D Ignition spark generator
5 Flame stabilisation E Fuel cut-off valve
6 Control mode F Flame indicator
7 After-running period
8 Control pause * ADR heaters < 40 s
9 Switching off

Malfunctions and troubleshooting | 6
9039412C Workshop manual TTP 120 _ 150 15 / 49
5.6 Fault switch-off
If the heater detects a malfunction, the indicator lamp flashes.
The malfunction must be located and rectified. To assist with
troubleshooting, see chapter6, "Malfunctions and
troubleshooting" on page 15.
6 Malfunctions and
troubleshooting
6.1 Basics
NOTE
Troubleshooting is generally restricted to locating faulty
heater components.
The following potential sources of malfunction are not
taken into account and should always be checked to
rule them out as the cause of fault:
uCorroded connector
uLoose plug connector
uCrimping defect at connector
uCompleteness of the connector
uCorroded cables and fuses
uCorroded battery terminals
uImpermissibly high ambient temperature
Carry out a function check in the vehicle after rectifying each
fault.
6.1.1 Diagnostics with Webasto Thermo Test
B
A
Fig.19 Diagnostics with WTT
A WTT USB interface B Diagnostic adapter
Connect and use the Webasto Thermo Test (WTT) USB
interface, diagnostic adapter and adapter cable as de-
scribed in the Operating Instructions.
The heater is diagnosable and can be tested with the WTT dia-
gnostic adapter and the WTT diagnostic software installed on a
PC/laptop when installed.
1. The diagnostic adapter is connected to the diagnostic con-
nector provided in the heater wiring harness (see
chapter10.6, "Wiring diagrams " on page 40).
2. The diagnostic adapter is connected to the WTT USB inter-
face.
3. The WTT USB interface is connected to the PC/laptop (at
least, USB 2.0 port).
4. Then, the WTT diagnostic software is started and the con-
nection is established to the heater.
For more information about the WTT and adapters, see
https://dealers.webasto.com.
NOTE
When the control element is connected via W-bus, dis-
connect the connector and connect the adapter plug.
After the diagnostics, reconnect the control element.
6.1.2 Fault lock-out and heater lock-out
Faults with the heater are detected by the control unit as a mal-
function and a fault after-run. Afterwards, the heater remains in
the fault lock-out. A fault code is output after detecting a mal-
function during the fault switch-off.
Procedure for analogue signals
The fault code is shown on the control element either by flash-
ing or by a letter combination on the display (depending on the
type of control element). The fault code assists in determining
the fault.
NOTE
If the fault lock-out is active, the heater can be restar-
ted using the control element after rectifying the fault.
See chapter6.4, "Instructions for cancelling the fault
lock-out" on page 16.
If the heater lock-out is active, switching on the
heater again does not restart it. See chapter6.5,
"Heater unlocking instructions" on page 17.
Procedure for digital signals (with WTT)
NOTE
Select in Webasto Thermo Test PC Diagnostics: Dia-
gnostics => Device Selection => W-bus.
Before removing the heater or add-on parts, always
print out the logs with the following data:
–– Operating and fault data.
–– Extended fault conditions.
(select in Webasto Thermo Test PC Diagnostics: Logs.)
NOTE
Always determine the cause of the lock-out first before
rectifying the lock-out.
6.2 Fault list on the control element
The fault codes of the heater are explained in chapter6.6,
"Overview of faults and fault codes" on page 17.
6.2.1 Switch (On/Off)
On control elements without a display (analogue), the fault
code is indicated in the form of a flash pulse.
Error code output:
After 5 fast flash pulses, the fault code is output by a sequence
of long flash pulses. The long flash pulses must be counted. This
number (fault code) provides information for the workshop
about the type of heater malfunction.

6 | Malfunctions and troubleshooting
16 / 49 9039412C Workshop manual TTP 120 _ 150
6.2.2 MultiControl / SmartControl / UniControl
Malfunctions are shown with fault codes in the display.
Error code output:
The fault code is indicated by a combination of digits and letters
(e.g. ‘H02‘ or ‘F05‘).
NOTE
Other fault codes (e.g. TXX) do not stem from the
heater and describe control element, system, or com-
munication faults.
6.3 Cause of malfunctions in the heater
and systems
A malfunction is caused when one or more faults occur. Pos-
sible faults are:
lOvervoltage / Undervoltage
lMalfunctions of components, e.g. due to short-circuit or
break
lThe overheating of heater
lImpermissible exhaust temperature
lunsuccessful starts,
lflame failure.
6.4 Instructions for cancelling the fault
lock-out
6.4.1 Analogue cancelling the fault lock-out
Switching on the heater (via control element).
There is a fault and it is detected by the control unit as a relevant mal-
function.
Heater shuts down due to the fault, i.e. fault switch-off followed by
fault lock-out. The fault code is shown on the control element.
Determine the cause of the fault
(e.g. with or without fault code output,
visual inspection of fuses and connectors, ...)
See also chapter6.6, "Overview of faults and fault codes" on
page 17.
Switch off heater.
Rectify the fault.
Switch on the heater.
Fault lock-out unlocked.
6.4.2 Digital cancelling the fault lock-out (with
WTT)
Connect diagnostic cable to the heater diagnostic plug (next to fuses).
Switch on the heater.
There is a fault and it is detected by the control unit as a relevant mal-
function.
Heater shuts down due to the fault, i.e. fault switch-off followed by
fault lock-out.
Determine error cause by reading out the fault code memory.
Click on the Fault list button to read out the fault code memory.
NOTE
Print out or note the fault code memory.
Rectify the fault.
Clear fault code memory with the command Clear fault code memory
or Heater lock-out in the Fault code memory menu.
Switch on the heater.
Fault lock-out unlocked.
NOTE
Certain faults add to the fault count in the fault code
memory. The heater assumes heater lock-out mode
when the number of faults in the fault code memory
exceeds a limit value. The maximum number of fault in
the fault code memory and the limit value of the fault
code memory is defined by the software.

Malfunctions and troubleshooting | 6
9039412C Workshop manual TTP 120 _ 150 17 / 49
6.5 Heater unlocking instructions
The heater can be unlocked with or without Webasto Thermo
Test PC diagnostics.
6.5.1 Analogue heater unlocking
NOTE
When on-board power supply is applied, never discon-
nect the connector from the heater.
The fault must be rectified.
To do so, follow these steps:
uSwitching on the heater (via control element).
uRemove fuse for at least 2s within 2s after switching on
(e.g. F3 on-board power supply of the vehicle).
uReinsert the fuse.
uSwitching off the heater (via control element).
6.5.2 Heater unlocking, digital (with WTT)
See chapter6.4.2, "Digital cancelling the fault lock-out (with
WTT)" on page 16.
6.6 Overview of faults and fault codes
NOTE
The control element can be connected via W-bus or
analogue (see wiring diagrams):
-W-bus connection: the HXX fault codes are shown in
the display.
- Analogue connection with display: the FXX fault codes
are shown in the display.
Analogue connection without display: the fault codes
are shown by the number of long flash pulses after the
5 short flash pulses.
NOTE
Hexadecimal fault codes
The letter "H" is shown on the control element before
the code, and in the WTT Diagnostics, the "h" is shown
at the end of the code. This means that, for example,
"H01" is equivalent to "01h".
NOTE
The heater can lock if several faults are registered. To
unlock the heater, see chapter chapter6.5, "Heater un-
locking instructions" on page 17.
All heater components are queried by the control unit.
The corresponding component must be checked first
when there is a defect. If it is OK, it must be assumed
that the control unit is defective.
NOTE
Replace component:
Within the warranty period, send in only the defective
component (not the entire heater) to Webasto.

6 | Malfunctions and troubleshooting
18 / 49 9039412C Workshop manual TTP 120 _ 150
6.6.1 Troubleshooting with error code output
*: Indicator lamp of control element flashing:
count the number of long flash pulses after 5 short flash pulses.
Analogue
fault code
Fault code
(hexa-
decimal)
Fault message /
Symptom
Possible causes Recommended action in workshop
F00
or
0*
H01
H07
H13
H16
H18
H20
H26
H81
H91
H92
H2C
H3F
HA0
HA6
HAC
HAD
HAE
No component fault Fuses 1. Check fuses:
F1, F2 and F3
Electrical wiring 2. Check battery connections:
At connector X2: - at pin 2 / + at pin 1 (heater
voltage)
3. Check control element and
test connector contacts:
W-bus connection:
contacts X4, pin 2
Analogue connection:
connector X4: + at pin 1 / + at pin 7
(if present)
Electrical wiring vehicle
blower
4. Check wiring of vehicle fan
for damage,
break and short-circuit,
see wiring diagram
Heater lock-out 5. Delete heater lock-out
(Rectify cause)
ADR function (if in-
stalled)
6. Check auxiliary drive input: S5,
Y2, see wiring diagram with ADR
7. Check Dynamo Plus input: X4,
pin 3 and pin 4
Battery disconnector
(BTS) (if available)
8. Check connections BTS
, replace BTS if necessary. See
wiring diagram with BTS
Control unit defective 9. Replace control unit
F01
or
1*
H02
H82
H83
No start Fuel supply 1. Check fuel supply (tank empty, fuel lines clogged)
2. Check fuel filter
3. Check tank extracting device and fuel line for
leaks
4. Bleed fuel system
Burner head 5. Check ignition electrode distance
6. Clean baffle plate, replace if necessary
7. Replace fuel nozzle
8. Fuel pump, check solenoid valve
9. Check fuel pump, replace if necessary
F02
or
2*
H03 Flame failure Fuel supply 1. Check fuel supply (tank empty, fuel lines clogged,
fuel line only partially filled)
2. Check fuel filter
3. Check tank extracting device and fuel line for
leaks
4. Bleed fuel system
Flame monitor 5. Flame monitor
Burner head 6. Clean baffle plate, replace if necessary
7. Replace fuel nozzle
8. Fuel pump, check solenoid valve
F03
or
3*
H04
H84
Overvoltage
or undervoltage
Power supply 1. Check battery
2. Check charging voltage
3. Check electrical connections
F04
or
4*
H05
H85
Flame was detected
prior to combustion
Fuel pump solenoid
valve defect
1. Visual check burner head, clean if necessary
2. Check solenoid valve
F05
or
H1A
H9A
Flame monitor Flame monitor defect Replace control unit

Malfunctions and troubleshooting | 6
9039412C Workshop manual TTP 120 _ 150 19 / 49
*: Indicator lamp of control element flashing:
count the number of long flash pulses after 5 short flash pulses.
Analogue
fault code
Fault code
(hexa-
decimal)
Fault message /
Symptom
Possible causes Recommended action in workshop
5*
F06
or
6*
H14
H93
H94
Short circuit of
coolant temperature
sensors
Coolant temperature
sensors wiring defective
1. Check wiring for damage and short-circuit
Coolant temperature
sensors
2. Carry out function check of coolant temperature
sensors, replace if necessary
F07
or
7*
H08
H88
Fuel pump solenoid
valve short-circuit in
electrical circuit
Fuel pump solenoid
valve defect
1. Check wiring and connector for damage, break
and short-circuit
2. Check solenoid valve, replace fuel pump if neces-
sary
F08
or
8*
H09
H15
H89
H95
Fan drive motor
short-circuit or break
Fan lock-up protection 1. Rectify cause of block and sluggishness
2. Check wiring and connector for damage, break
and short-circuit
3. Check operation of drive motor, replace if neces-
sary
F09
or
9*
H19
H99
H2E
Ignition spark circuit
is defective
Ignition spark generator 1. Check wiring and connector for damage, break
and short-circuit
2. Check ignition spark generator, replace if neces-
sary
F10
or
10*
H06 Heater overheats Coolant temperature
sensors defective
1. Check wiring for damage, break and short-circuit
2. Measure resistance of coolant temperature
sensors, replace coolant temperature sensors if ne-
cessary
Coolant system 3. Check coolant level, bleed coolant circuit
4. Carry out function check of coolant pump, re-
place if necessary
5. Check wiring and connector for damage, break
and short-circuit
F11
or
11*
H0B
HC0
HC1
HC2
HC3
HC4
Coolant pump short-
circuit or break
Coolant system 1. Check coolant level
2. Check coolant flow
3. Bleed coolant pump. Rectify possible cause
4. Check anti-freeze in the coolant, change coolant
if necessary
Coolant pump defective 5. Check wiring for damage, break and short-circuit
6. Carry out function check of the coolant pump,
replace if necessary
F14
or
14*
H1B
HAB
Coolant temperature
sensors breaks or
short-circuits
Wiring defective 1. Check coolant temperature sensor wiring and
connector for damage
Coolant temperature
sensors defective
2. Check coolant temperature sensors
F16
or
16*
H4F
H5B
Exhaust gas temper-
ature too high
Exhaust gas temperat-
ure sensor defective
1. Check wiring and connector of exhaust gas tem-
perature sensor for damage, replace if necessary
2. Measure resistance of exhaust gas temperature
sensor, replacing if necessary
Heater fouled 3. Visual inspection with cleaning of inner surface of
heat exchanger, replace if necessary
Ambient temperature of
heater too high
4. Allow the heater to cool down, check temperat-
ure and ventilation of installation space (see installa-
tion instructions)
Control unit defective 5. Replace control unit
F17
or
17*
H4D
H31
Exhaust gas temper-
ature sensor
Wiring defective 1. Check wiring and connector for damage, break
and short-circuit

6 | Malfunctions and troubleshooting
20 / 49 9039412C Workshop manual TTP 120 _ 150
*: Indicator lamp of control element flashing:
count the number of long flash pulses after 5 short flash pulses.
Analogue
fault code
Fault code
(hexa-
decimal)
Fault message /
Symptom
Possible causes Recommended action in workshop
Exhaust gas temperat-
ure sensor defective
2. Check exhaust gas temperature sensor, replace if
necessary
Heater fouled 3. Visual inspection with cleaning of inner surface of
heat exchanger and combustion tube, replace if ne-
cessary
F20
or
20*
H25
HA5
No fuel preheating Heater cartridge wiring
defective
1. Check wiring and connector for damage, break
and short-circuit
Heater cartridge defect-
ive
2. Check operation of heater cartridge, replace if
necessary
* The number of long pulses corresponds to the number of the fault code.
6.6.2 Troubleshooting without error code output
NOTE
We generally recommend the following procedure:
uCheck fuses
uCheck operating voltage
uCheck for damage and ensure passages are clear:
–– combustion air intake
–– exhaust pipe
–– fuel line
uAlso check condition of filter.
Symptom Possible cause Possible troubleshooting Comments / Service
Heater does not respond, no
component running. Indicator
lamp not flashing.
Operating voltage 1. Fuse blown
uRectify cause, change fuse
2. Unlock heater
The indicator lamp is provided
by the heater (see wiring dia-
gram). Check / replace control
element.
3. Supply voltage to heater con-
nector
uMeasure voltage
Indicator lamp (control ele-
ment, Quick Heating button)
1. Control element fuse blown
uRectify cause, change fuse
2. Supply voltage on control
element (switch with function
display)
uMeasure voltage at pin
3. Continuity at control element
(switch with function display)
uCheck pin to ground
4. Control element indicator
lamp defective
uReplace control element if
necessary