Valeo Thermo H 160 Instruction manual

Rev. 03/2019
Id.No. 11123930B
Thermo H 160
Thermo H 230
Thermo H 300
Thermo H 350
Workshop Manual
HEATING SYSTEMS

1
Thermo H Content
1 Introduction
1.1 Content and purpose 101
1.2 Effectivity of the workshop manual 101
1.3 Meaning of highlighted content 101
1.4 Symbols 101
1.5 Further documentation to be used 101
1.6 Safety information and regulations 101
1.6.1 Required qualifications 102
1.6.2 Emergency stop / de-energizing 102
1.6.3 Work at the heater 102
1.7 Suggestions for improvement and change 102
2 Technical data
2.1 Fuel 202
3 Description of assemblies and components
3.1 HV control head 302
3.1.1 Small distribution board 302
3.2 Heat exchanger 303
3.2.1 Combustion chamber 303
3.2.2 Heating cartridges 303
3.3 Diesel burner head 304
4 Functions of the heater
4.1 General functional description of the heater 401
4.2 HV heater 401
4.2.1 Switching on 401
4.2.2 Heating operation 401
4.2.3 Switching off 401
4.3 D heater 402
4.3.1 Switching on and start 403
4.3.2 Heating operation 403
4.3.3 Switching off 404
4.3.4 Diagnosis interface and DTT diagnosis 405
4.3.5 Test plug 405
4.3.6 Malfunction interlock and heater interlock 405
4.3.7 Error output 408
5 Troubleshooting and error correction
5.1 General 501
5.2 HV heater troubleshooting 501
5.3 D heater troubleshooting 502
6 Wiring diagrams
6.1 General 601
6.2 HV heater 601
6.3 D heater 611

2
Thermo H Content
7 Servicing
7.1 General 701
7.1.1 Heater servicing 701
7.2 HV heater servicing 701
7.3 D heater servicing 701
8 Components and heater removal and installation
8.1 General 801
8.2 HV control head 802
8.2.1 Temperature guards (temperature limiter, control thermostat) removal/installation. 802
8.2.2 Hood removal/installation 803
8.2.3 Housing removal/installation (incl. cable connections) 803
8.2.4 Small distribution board removal/installation 803
8.2.5 Heating cartrides/screw plugs removal/installation 804
8.2.6 HV DC wiring harness removal/installation 806
8.2.7 HV AC wiring harness removal/installation 807
8.2.8 LV DC control wiring harness removal/installation 807
8.2.9 Pump harness harness removal/installation 808
8.3 Diesel burner head 809
8.3.1 Burner removal/installation 809
8.3.2 Removal/installation of the temperature sensor with integrated overheating protection 810
8.3.3 Hood removal/installation 810
8.3.4 Combustion air fan removal/installation 811
8.4 Heat exchanger removal/installation 812
8.5 Heater removal/installation 812
8.6 Start-up after burner or heater installation 814
8.6.1 Bleeding the fuel system 814
8.6.2 Bleeding of the coolant circuit 814
9 Modifications and retrofits
9.1 General 901
10 Packing/storage/shipping
10.1 General 1001

101
Thermo H 1 Introduction
1Introduction
1.1 Content and purpose
This workshop manual is used during maintenance and
repair of water heaters (further referred to as heaters)
Thermo H.
Electrical work may only be performed by persons,
which have the required qualification (see 1.6.1).
ATTENTION:
Work on the heater may only be performed by briefed
and/or trained by Valeo personnel.
1.2 Effectivity of the workshop manual
The workshop manual applies to heaters listed on the title
page of this document.
It may be subjected to modifications and amendments.
The respectively currently effectife version is binding. This
version can be found on the Valeo homepage under
www.valeo-thermalbus.com/eu_en/Service/Downloads/
Heating-systems/Thermo-H.
1.3 Meaning of highlighted content
Throughout this manual the emphasized words Warning!,
Caution!, ATTENTION: and NOTE: used as follows:
This caption is used to indicate possible severe inju-
ries or fatal accidents if instructions or procedures
are carried out incorrectly or entirely disregarded.
This caption is used to indicate possible minor inju-
ries if instructions or procedures are carried out
incorrectly or entirely disregarded.
ATTENTION:
This caption points to actions which may cause ma-
terial damage.
NOTE:
This caption is used to draw attention to an important
feature.
1.4 Symbols
1.5 Further documentation to be used
The use of additional service literature is required.
References are provided in the workshop manual at
appropriate locations.
Use the following documents during operation and main-
tenance of the heaters:
• Installation and operating instructions
• Spare parts list
• Technical Information (TI)
• Workshop Manual Thermo S
This service literature is also available at www.valeo-ther-
malbus.com/eu_en/Service/Downloads/Heating-systems
for download.
1.6 Safety information and regulations
Basically, general accident pevention provisions and the
valid industrial safety directions must be adhered to.
"General Safety Regulations" which exceed the frame-
work of these provisions are listed below.
The specific safety regulations which affect the present
manual are issued highlighted in the individual sections or
procedures.
Danger to life and health!
Warning!
Danger to life and health!
Warning!
Hazardous to health!
Caution!
Symbol tightening torque value:
Identifies in graphics parts (eg nuts, bolts)
that are to be mounted with a specific tigh-
tening torque. The torque values are
shown at the symbol and are binding.
Orientation help - next wor-
king step (s) on the HV
control head.
Orientation help - next wor-
king step (s) on the heat
exchanger.
Orientation help - next wor-
king step (s) on the Diesel
burner head.

102
Thermo H 1 Introduction
1.6.1 Required qualifications
Electrical work may only be performed by a qualified
electrician for HV systems in motor vehicles, crafts-
man, activity with repetitive character. Training acc.
to DGUV 200-005 (previously BGI 8686)
NOTE:
The provisions of these Regulations are binding within the
territory governed by DGUV Regulations and should
similarly be observed in countries without specific regula-
tions.
Even before the start of non-electrical work, the
voltage- freeness must be determined by a skilled
electrician.
1.6.2 Emergency stop / de-energizing
The Thermo H heater itself does not have an emergency
stop system. It‘s control and power supply is integrated
into the vehicle's electrical system.
It is therefore the responsibility of the user to inform
himself before the commisioning of the heater in the
vehicle how the heater can be successfully de-energized
if necessary (maintenance, service work, abnormal beha-
vior etc.).
1.6.3 Work at the heater
Installation, maintenance and repairs may only be
carried out when the vehicle's engine is not running
and the high voltage supply (AC/DC) / power supply is
switched off.
Before starting the work at the heater, it is to make
voltageless acc. to DIN VDE 0105-100 and this state
must be ensured for the duration of the work.
The following safety precautions must be observed:
– switch off the power supply to the heater
– ensure it cannot be switched on again
– verify system is voltage-free, all poles
– ground and short circuit (the de-energized circuit)
– cover or block neighbouring parts under voltage
Electrical cables and operating elements of the heater
must be arranged in the vehicle in such a way that
their functioning is faultless under normal operating
conditions and cannot be hampered.
Work at electrical equipment may only be started if
protective measures against electric shock, short
circuits and arcing faults have been carried out.
Familiarize yourself with the Thermo H Installation
Instructions before you make any modifications to the
existing heater installation.
NOTE:
The Installation and operating instructions contain the
statutory regulations and other safety hints and regula-
tions for the proper installation of the heater.
Further they contain safety instructions and regulations to
be followed for safe operation of the heater.
1.7 Suggestions for improvement and
change
Please direct any complaints, improvement or modifica-
tion suggestions regarding this manual to:
service-valeo[email protected]
High voltage!
Danger to life!
Warning!
High voltage!
Danger to life!
Warning!
High voltage!
Danger to life!
Warning!
Danger to life and health!
Warning!

201
Thermo H 2 Technical data
2 Technical data
Except where limit values are specified, these technical
data refer to the usual heater tolerances of ±10% at an
ambient temperature of +20°C and at the rated voltage.
Technical data:
Heater (general)
Kind of design Hybrid heater
Ambient temperature during operation °C -40 up to +85
Storage temperature °C -40 up to +85
Operating overpressure max. bar 2.0
Dimensions (tolerance +/- 3 mm) mm Lenth: 828
Width: 274
Height: 350
Weight kg 32
Capacity of the heat exchanger l 7
Minimum water flow l/h >1500 *
Minimum capacity of the water system l 35
Antifreeze ratio in the cooling system % 30 up to 60
* Depending on the heat flow taken by the vehicle, a minimum burner operation
of 120 seconds should be achieved.
Electrical part (high voltage)
Device version AC070 AC090 AC140 AC200 DC070 DC070 DC200 DC140
Nominal heating flow max. kW 7 9 14 20 7 7 20 2x 7
Rated voltage V 400 690 600 690 600
Rated control voltage V 24
Control voltage min. V 20.4 16
Control voltage max. V 26.4 32
Power consumption kW 7 9 14 20 7 7 20 2x 7
Frequency Hz 50-60 --
Rated current A 9.9 13.5 19,75 29.6 9.9 11.8 29.6 2x 11.8
Electrical protection A 16 16 25 32 16 16 35 2x 18

202
Thermo H 2 Technical data
Optional Fuel Filter Heater NOTE:
Circulating pumps must be assigned to the heaters accor-
ding to the flow resistance in the coolant circulation sys-
tem.
2.1 Fuel
Suitable fuel is the diesel fuel specified by the vehicle ma-
nufacturer. Only the on the model plate of the heater
specified fuel must be used.
The following table lists the by Valeo approved fuels and
their specifications.
*Further information on approved by Valeo fuels con-
tains the TI (Technical Information) Fuels.
It can be found on the Valeo homepage under Service/
Technical Updates (TI)/Heating systems.
In case of air temperatures below 0°C a commercial avail-
able winter Diesel fuel must be used.
The usage of flow improvers respectively additives is per-
mitted. There are no negative influences due to additives
known.
ATTENTION:
While using the fuels, their operating limits must be
considered and if necessary, suitable measures
(nozzle preheating, electrical heated filter) should be
applied.
If fuel is supplied from the vehicle tank, follow the
vehicle manufacturer’s instructions on additives.
Diesel part
Thermo H 160 230 300 350
Heating flow (at ambient
temperature of 20°C )
kW
kcal/h
16
13800
23
20000
30
26000
35
30000
Fuel Diesel
Fuel consumption kg/h 1.62.53.03.6
Rated voltage V 24
Operation voltage range V 20 - 30
Electrical power consumption at 24V W 50 65 90 120
Max. permitted temperature of sucked
combustion air
°C +85
CO2in exhaust gas at rated voltage Vol % 9.5 + 1.5
Filter heater
Rated power consumption W 240
Rated voltage V 24
Switch-on point C° 0.5 ± 2.5
Switch-off point C° 5.5 ± 2.5
Fuel Requirements
acc.
Summer diesel DIN EN 590
Winter diesel DIN EN 590
Arctic diesel and Diesel for a strong
winter climate
DIN EN 590
Bio diesel (FAME)*DIN EN 12214
Paraffinic diesel fuel from synthesis
or hydrogenation (HVO)*DIN EN 15940

301
Thermo H 3 Description of assemblies and components
3 Description of assemblies and components
The water heater, hereafter referred to as heater, is used
in conjunction with the vehicle’s own heating system
– to heat the passenger compartment,
– to defrost the vehicle windows and
– for pre-heating
The water heater operates independently from the vehicle
engine and is connected to the cooling system, the fuel
system and the electrical system of the vehicle. It is bolted
down to the vehicle chassis or is secured using an addi-
tional cross beam.
The hybrid function of the heater includes the generation
of heat
a) by burning liquid fuel, and
b) by electric current.
The diesel burner head (see Fig. 301) is responsible for
heat generation by combustion - the control head AC / DC
with the connected heating cartridges for the generation of
heat by electric current.
Both systems for heat generation operate independently
of one another and can be operated simultaneously or
individually.
The heat is transferred to the coolant circuit of the vehicle
via the heat exchanger of the heater. The adaptation to
the changing heat demand is done by intermittent opera-
tion (intermittent mode).
Fig. 301 Heater - Overview
Heat exchanger
Diesel burner head
HV Control head

302
Thermo H 3 Description of assemblies and components
3.1 HV control head
The AC/DC control head (see Fig. 302) consists of an
aluminum die-cast ring as housing (4) and the hood (1).
Inside is a small distribution board (3) behind a stabilizer
(2). The housing (4) is screwed to the heat exchanger (8) .
3.1.1 Small distribution board
The small distribution board (3, Fig. 302) includes the
components required for the electrical part of the heater
which are mounted on a 35mm top hat rail.
The top hat rail is attached to the heat exchanger (8) via
stud bolts.
Fig. 302 HV control head / Small distributor board
1 Hood
2 Stabilizer
3 Small distribution board
4 Housing with cable glands
5 Control thermostat
6 Temperature limiter
7 Heating cartridges
8 Heat exchanger
1
2
3
4
7
8
5
6

303
Thermo H 3 Description of assemblies and components
3.2 Heat exchanger
In the heat exchanger (1, Fig. 303) the water flowing
through is heated directly by heating cartridges (7) arran-
ged in a ring shape.
The water is also heated via the inner wall (15) of the heat
exchanger when the diesel burner head is in operation.
The hot exhaust gases resulting from the combustion are
conducted on the inner wall via lamellas (5) and thus give
off heat to them.
The cylindrically welded construction has a water inlet (3)
and a water outlet (11). The heater is integrated into the
cooling water circuit via these two connection ports.
In the water inlet is the control thermostat (12) for the
electrical part of the heater installed.
The temperature limiter (13) for the electrical part and the
control thermostat (14) for the control of the diesel burner
head are located in the wall of the heat exchanger. The
plate at the front has receiving openings with threads for
the heating cartridges. At the rear, the Diesel burner head
is fixed.
3.2.1 Combustion chamber
The combustion chamber (8, Fig. 303) is located inside
the heat exchanger. In it the combustion of the diesel-air
mixture produced by the diesel burner head takes place.
After exiting the combustion chamber, the hot exhaust
gases are deflected and passed through fins (5) which are
located on the inner wall of the water-conducting part of
the heat exchanger.
3.2.2 Heating cartridges
At the end of the rod-shaped, water-proof heating cart-
ridges (6, Fig. 302 and 7, Fig. 303) there is an external
thread with a hexagon for screwing in and the electrical
cables are led out.
Fig. 303 Heat exchanger
1 Heat exchanger outer wall
2 Bleed screw
3 Water inlet
4 Device attachment
5 Lamellae
6 Exhaust gas outlet
7 Heating cartridge (6x)
8 Combustion chamber
9 water-carrying area
10 Blind plugs (3x)
11 Water outlet
12 Control thermostat (HV control
head)
13 Temperature limiter (HV control
head)
14 Control thermostat (Diesel
burner head)
15 Heat exchanger inner wall
1
2
3
5
4
6
7
8
9
10
7
11
12
13
14
15

304
Thermo H 3 Description of assemblies and components
3.3 Diesel burner head
The diesel burner head is used to generate the diesel-air
mixture, which is burned in the combustion chamber.
Components for the control of the combustion process are
integrated.
Further information can be found in Chapter 3 of the
Workshop Manual for the Thermo S series heaters. See
also 1.5.

401
Thermo H 4 Functions of the heater
4 Functions of the heater
4.1 General functional description of the
heater
The Thermo H hybrid heater integrates two different and
independent each other coolant heating systems:
1. Generation of heat by burning liquid fuel via the diesel
burner head - further referred to as D heater.
2. Generation of heat by electrically operated heating
cartridges via the HV control head - further referred to
as HV heater.
Both transmit heat to the coolant circuit via the common
heat exchanger.
Also the function and control of the two systems is inde-
pendent of each other and is therefore also explained
separately for the systems.
4.2 HV heater
NOTE:
The following functional sequence applies to the opera-
tion of the HV heater with AC or DC or both.
4.2.1 Switching on
24V DC must be connected to the HV control wiring
harness for external control by an operating or control
element (for example, switch, relay, pre-selection timer)
installed on the vehicle in order to switch on the HV
heater.
This power is fed to the load contactor(s), the control ther-
mostat and the overheat protection (see 3.2).
They constitute the control loop of the HV control head.
If all of the following three conditions are met:
1. 24V DC is applied to the external control input,
2. The control thermostat has not yet reached the upper
switching threshold / has fallen below the lower swit-
ching threshold,
3. The overheating protection has not yet reached the
upper switching threshold,
the respective contactor is activated, the moving core
attracts and closes the main contacts.
In this way the heating cartridges connected to the
contactor are powered.
The heating cartridges now convert the electrical energy
into heat.
4.2.2 Heating operation
The control thermostat opens its contact at 75°C and
closes it again at 68°C. In this way, the heating operation
is regulated.
The overheat protection opens its contact at 125°C and
must be mechanically reset by service personnel.
ATTENTION:
After the overheating protection has been triggered,
the cause of the overheating must first be removed
before it is reset.
4.2.3 Switching off
When the 24V DC control voltage at the external control
terminal is interrupted by a vehicle installed control
element (e.g. switch, relay, pre-selection timer), the load
contactor opens and the voltage supply of the heating
cartridges is switched off.
The circulating pump in the coolant circuit continues its
operation for approx. 120s.

402
Thermo H 4 Functions of the heater
4.3 D heater
The function of the heater is based on the principle of the
high-pressure atomizer burner and is monitored by an
integrated control unit.
The burner motor powers the fan and the fuel pump. The
fuel pump is coupled to the motor using a plastic coupling.
The fan produces the required combustion air, the combustion
air volume is impacted by the burner motor speed.
The speed is monitored by a sensor in the control unit, which analy-
ses the changing magnetic field of the magnets in the coupling.
The speed required for the CO
2
-content is determined during
first calibration at Valeo and is stored in the control unit.
In a maintenance event the workshop can adjust the CO2
setting using the DTT diagnosis (Diagnose Thermo Test).
The fuel pressure is generated in the fuel pump and reduced
to the required pressure using a pressure limiting valve.
A solenoid valve releases the fuel via the atomizer nozzle
for combustion in the combustion chamber.
As an option, the fuel pump can be equipped with a nozzle
block preheater. The nozzle
block preheater heats the
nozzle holder with the atomizer nozzle at low temperatures,
and thus the fuel. The fuel air mixture is ignited in the
combustion chamber via a high-voltage ignition spark.
The flame is monitored by a flame detector integrated into
the control unit.
Depending on the equipment, the heater is switched on
and off using a
• pre-selection timer
•switch
• or climate control.
During heating operation the burner is automatically
switched on and off. The heater is switched on, when the
temperature falls short of a lower temperature threshold,
and is switched off, if the upper temperature threshold is
reached (see table Table 401).
The switching thresholds depend on the heater variant
and the heating operation type. They cannot be changed
and are programmed into the control unit.
For overheating protection of the heater the switching
thresholds are modified by the control unit, if specified
temperature gradients are exceeded.
If the specified minimum burning duration is not reached,
the switching thresholds will be reduced. This protects the
heater against sooting of the heat exchanger.
An operating display is available for monitoring the operating
status. A flame indication can be optionally installed.
The operating display is also used to output error
messages in flash code.
It is also possible to read the flash code via the two-pin
plug in the heater wiring harness (see 4.3.7).
Use max. 2W lamps.
Table 401 Standard switching thresholds
Standard
Lower switching threshold: auxiliary heating in °C 78
NOTE
Switching thresholds may deviate
per customer.
Upper switching threshold: auxiliary heating in °C 85
Lower switching threshold: normal mode parking heating in °C 70
Upper switching threshold: normal mode parking heating in °C 85
Lower switching threshold: saving mode 1 parking
heating in °C
55
Upper switching threshold: saving mode 1 parking
heating in °C
70
Lower switching threshold: saving mode 2 parking
heating in °C
45
Upper switching threshold: saving mode 2 parking
heating in °C
60

403
Thermo H 4 Functions of the heater
Operational heater sequence
4.3.1 Switching on and start
When switched on, the operating display is illuminated,
the control unit starts controlled operation and checks the
coolant temperature.
If the coolant temperature is below the upper temperature
threshold, the initial cycle starts.
Combustion air fan and circulating pump are switched on.
After approx. 12 seconds (initial cycle time) the high-
voltage spark is ignited. Approx. 1 second later the
solenoid valve in the fuel pump is opened.
The fuel injected via the atomizer nozzle and mixed with
the air of the combustion air fan, is ignited by the ignition
spark and burned in the combustion chamber.
The flame is monitored by a flame detector integrated into
the control unit.
A few seconds after a flame is detected, the control unit
switches the electronic ignition unit off. Until then the
flame is stabilised. The heater is not yet in heating mode.
With optional nozzle block preheater:
The integrated temperature sensor determines the
temperature on the nozzle holder as soon as the initial
cycle starts. Starting at a temperature of < 5°C the nozzle
block preheater is switched on. Depending on the
determined temperature and the vehicle electrical system
voltage the preheating time is determined. The duty cycle
is limited to a maximum of 120 seconds.
The burner motor does not run during the entire
preheating time. It starts latest 12 seconds prior to
expiration of the determined preheating time during initial
cycle.
The initial cycle time can be extended to a maximum of
120 seconds.
The further sequence takes place as described.
4.3.2 Heating operation
After the flame is stabilised, the heater is in controlled
(normal) operation.
Depending on the coolant temperature, the coolant
temperature is maintained at one level by switching the
burner alternately on and off.
Once the upper switching threshold is exceeded, heating
operation is finished and run-down initiated.
The solenoid valve is closed, the flame expires, however the
combustion air fan and circulating pump continue running.
The run-down ends approx. after 120 seconds. The
combustion air fan is switched off.
The heater is in a controlled break.
The operating display is illuminated.
Once the temperature falls short of the lower switching
threshold, the heater restarts burner operation. It runs
through the same sequence as the switching-on
Fig. 401 D-Heater Operational sequence
Signals
Main switch off on off
Terminal 61 off (parking heating) on (auxiliary heating) off (parking heating)
Coolant temperature T > T_min T < T_min T >= T_max T < T_min T >= T_max T < T_min
UPFA on UPFA off
Flame
generation
Flame
generation
Flame
generation
Actuators
Operating display
Flame display
Combustion air motor
Circulating pump
Electronic ignition unit
Solenoid valve
Nozzle block preheater
Time in s 0..108 12 1 0..15 5 ... 30 90 0..108 12 1 0..15 5 ... 30 90 0..108 12 1 0..15 5 ... 30 90
State
Look for Optional nozzle block preheating Initial cycle with light check Pre-ignition Ignition Stabilisation Run-down with safety period Run-down 2 Optional nozzle block preheating Initial cycle with light check Pre-ignition Ignition Stabilisation Run-down with safety period Run-down 2 Optional nozzle block preheating Initial cycle with light check Pre-ignition Ignition Stabilisation Run-down with safety period Run-down 2
OFF Standby Start Heating Run-
down
Standby Start Heating Run-
down
Standby Start Heating Run-
down
Off

404
Thermo H 4 Functions of the heater
sequence.
Different switching thresholds are defined for different
heater operating modes.
The switching thresholds are selected depending on the
present condition and the selected heating operation.
The following switching thresholds may be applied.
• Parking heating mode and auxiliary heating mode
• Gradient evaluation
• Minimum combustion period (also called hysteresis
adaptation)
• Saving mode 1 and saving mode 2
The switching thresholds can be obtained from Table 401.
4.3.2.1 Auxiliary heating mode and parking
heating mode
The control unit received the information, whether the
vehicle engine is running or not, from terminal D+/+61.
If terminal D+/+61 is connected and the vehicle engine is
running, the switching thresholds in auxiliary heating
mode are higher than in parking heating mode with the
engine not running.
In that case a saving mode is activated in parking heating
operation.
If terminal D+/+61 is not connected, then there is no
distinction. The heater always runs in parking heating
operation.
4.3.2.2 Saving modes
Two different saving modes are programmed in the
control unit.
Saving mode 1 and saving mode 2 exist (see Table 401).
In saving mode 1 the switching thresholds are higher than
in saving mode 2.
If saving mode is activated, the controlled temperatures in
the heating system are maintained at a low temperature
level. The lower and upper switching threshold are
reduced.
Due to lower radiation loss the fuel consumption can be
reduced for a lower heat demand (e.g. warmer mode).
The heater burner output is not reduced.
In auxiliary heating mode (signal from terminal D+/+61)
saving mode is automatically deactivated.
4.3.2.3 Gradient evaluation
In case of low coolant flow or poor coolant circuit venting
the temperature quickly increases in heating operation.
The control unit recognises the quick temperature
increase and automatically sets the upper switching
threshold to a lower value.
The quicker the temperature increases, the lower the
switching threshold for starting the controlled break is set.
In addition, the burner is also switched back on again after
the controlled break at a lower switching threshold.
This prevents residual heat triggering the overheating
protection.
4.3.2.4 Minimum combustion period
A minimum burner combustion period of 120 second is
targeted.
For ambient and operating conditions this target is not
always achieved.
In order to achieve the minimum combustion period, the
lower switching threshold is variably adjusted by the
control unit.
This process is also called hysteresis adaptation and is
applied in parking heating operation as well as auxiliary
heating operation.
If the combustion period falls short of the minimum
combustion period, the lower switching value is lowered
by 1K for the following combustion process.
The upper switching threshold remains as is.
This can be repeated until the minimum combustion
period is reached or the lower switching threshold is
reduced by 5K.
Further lowering is not possible.
Following a combustion process, where the required
minimum combustion period was reached, the lower
switching value is reset to its original value.
4.3.3 Switching off
Switching the heater off ends the combustion process.
The operating display expires and run-down is initiated.
The solenoid valve closes, the flame expires, the
combustion air fan and circulating pump continue running.
The run-down ends approx. after 120 seconds. The
combustion air fan is switched off.
If a malfunction occurs during run-down (e.g. flame
detection), the run-down may be shorter than 120 seconds.
During run-down it is permitted to switch the heater
back on. The burner will restart after a run-down time
of 30 seconds and subsequent initial cycle time.

405
Thermo H 4 Functions of the heater
4.3.4 Diagnosis interface and DTT diagnosis
The D heater supports diagnosis capabilities.
Using the DTT diagnosis adapter, DTT diagnosis and a
PC, the heaters can be checked in the vehicle. For this
purpose the DTT diagnosis adapter is connected to the
diagnosis interface in the heater wiring harness, and to a
PC (see Fig. 403).
Next, DTT diagnosis is started on the PC and the connec-
tion to the heater control unit is established.
4.3.5 Test plug
During tests with the DTT diagnosis menu "component
test", the test plug is plugged directly into the control unit
of the heater after removal of the hood instead of the tem-
perature sensor.
NOTE
For protection against moisture and contamination ensure
that the diagnosis interface is sealed using protective
caps, if not in use.
The latest DTT diagnosis software can be found in the
Internet on the Valeo homepage under Service/
Downloads/Heating Systems/Diagnostic-Preheater-Fuel-
Filter-Software.
4.3.6 Malfunction interlock and heater interlock
Malfunction interlocks and heater interlocks are distin-
guished.
Each malfunction interlock and heater interlock is stored
in the control unit.
The heater should be protected against thermal loads.
Fig. 402 Test plug
Fig. 403 DTT diagnosis connection to the heater
24V
BUSY
PC SpherosThermoTest
ca.3m
Kabel
zum Fahrzeug
Thermo H
Heater wiring harness
Diagnostic interface
to vehicle
approx.
3 m cable

406
Thermo H 4 Functions of the heater
Thermal loads can be triggered by:
• Coolant flow too low
• Coolant circuit not or only partially filled /
dry overheating.
• Circulating pump failure.
The control unit software detects overheating.
4.3.6.1 Malfunction interlock
If one of the malfunctions listed below occurs, the heater
will initiate a fault shut-down, followed by malfunction
interlock.
Depending on the error timing, no run-down or a 120 seconds
run-down will be executed.
Flash impulses are outputted via the operation indicator.
In case of several sequential malfunction interlocks a
heater interlock is initiated (see 4.3.6.2).
Malfunctions during switching-on and start proce-
dure
NOTE:
If malfunctions occur during switching-on or during the
start process prior to ignition, the heater will be switched
off without run-down.
The heater is in malfunction interlock.
The motor stops immediately or does not start.
If the circulating pump is externally actuated, it will
continue operating.
Malfunction criteria:
• Short circuit and/or interruption of electrical
components:
– Burner motor (stops immediately)
– Circulating pump
– Electronic ignition unit
– Optional nozzle block preheater
• Flame or extraneous light detection by the flame
detector prior to ignition of the high-voltage ignition
spark.
• No start: No flame detection within 15 seconds
after opening the solenoid valve.
• Temperature sensor delivers unacceptable
temperature values.
• Heater operation outside the permissible temperature
range.
• Burner motor speed signal faulty.
• Voltage falling short of the low voltage threshold of
approx. 20.5 V at motor start or within a duration of 20
seconds after a heating request.
• Voltage exceeding the high voltage threshold of approx.
30 V at motor start or within a duration of 6 seconds (run-
down only, no malfunction interlock).
Malfunctions during heater operation
NOTE:
In case of malfunctions during heater operation, a
120 seconds run-down will be executed first. Subsequently
the heater status is switched to malfunction interlock.
If the circulating pump is externally actuated, it will
continue operating.
Malfunction criteria:
• Short circuit and/or interruption of electrical
components:
– Burner motor (stops immediately)
– Circulating pump.
• Water temperature greater than the upper switching
threshold.
• Temperature sensor delivers unacceptable
temperature values.
• Heater operation outside the permissible temperature
range.
• Burner motor speed signal faulty.
• Flame interruption (combustion interruption for longer
than 15 seconds).
• Voltage falling short of the low voltage threshold of
approx. 20.5 V at motor start or within a duration of
20 seconds after a heating request.
• Voltage exceeding the high voltage threshold of approx.
30 V at motor start or within a duration of 6 seconds (run-
down is applied, but no malfunction interlock).
• Control unit malfunction.
Malfunctions during run-down
NOTE:
If the circulating pump is externally actuated, it will
continue operating.
Malfunction causes:
• Short circuit and/or interruption of electrical components:
– Burner motor (stops immediately)
– Circulating pump (if the CP interruption monitoring
is activated)
• Heater operation outside the permissible temperature
range.
• Motor speed signal faulty.
• Voltage falling short of the low voltage threshold of
approx. 20.5 V at motor start or within a duration of
20 seconds after a heating request.
• Voltage exceeding the high voltage threshold of approx.
30 V at motor start or within a duration of 6 seconds
(run-down is applied, but no malfunction interlock).
• Control unit malfunction.

407
Thermo H 4 Functions of the heater
Malfunction interlock release
The malfunction interlock is released when the heater is
switched off.
After that it will be immediately ready for operation.
Deleting the error using the diagnosis
The detected error is stored in the error memory and can
be read out using the DTT diagnosis.
It is possible to delete the stored error using the DTT
diagnosis.
4.3.6.2 Heater interlock
The heater interlock overrides the standard
malfunction interlock.
If the heater interlock is active, neither start nor run-down
are executed after switching the heater on again.
Prior to restarting the heater troubleshooting must be
performed by personnel trained by Valeo in order to
identify and remedy the cause.
After that the heater interlock can be released (see
below).
Here it is differentiated between interlocks caused by
overheating and interlocks caused by other errors.
NOTE:
If malfunctions occur during switching-on or during the
start process prior to ignition, the heater will be switched
off without run-down.
The heater is in heater interlock state.
The burner motor stops immediately or does not start.
Besides that a run-down between 30 seconds and up to 120
seconds is performed depending on error type and timing.
Subsequently the heater status is switched to heater interlock.
If the circulating pump is externally actuated, it will
continue operating.
Heater interlock causes:
• Short circuit and/or interruption of electrical
components:
– Solenoid valve
– Flame detector
– Overheating protection
– Disconnection of the water temperature sensor
(overheat protection / temperature sensor)
• The flame is not expired within 30 seconds after the
run-down was started (Burner motor stops).
• Overheating protection triggered.
• Control unit error
• Repeated malfunctions
• Repeated flame interruptions
Heater interlock release
ATTENTION:
A distinction is made between heaters with standard
control (pre-selection timer, switch, etc.) and heaters
controlled via a CAN bus.
Heaters with standard control
To release the heater interlock the heater must be discon-
nected one time from the vehicle electrical system.
Heater interlock release procedure:
1. Remedy the cause of the heater interlock.
2. Switch on the interlocked heater.
3. Disconnect the switched on heater from the vehicle
electrical system.
4. Reconnect the switched on heater to the vehicle
electrical system.
NOTE:
The heater starts after reconnection to the vehicle electri-
cal system automatically.
The heater can be switched off during initial cycle.
Heater interlock release using the DTT diagnosis:
1. Connect the heater with the DTT diagnosis and read
out the error memory.
2. Correct the cause of the heater interlock.
3. Disconnect the heater from the vehicle electrical
system.
4. Reconnect the heater to the vehicle electrical system.
5. Clear the error memory using the DTT diagnosis.
Heaters with control via CAN bus
Heater interlock release by pulling the fuse:
ATTENTION:
It is not allowed to disconnect the heater from the
vehicle mains by pulling the heater connector under
power.
1. Disconnect the switched-on and interlocked heater
from the vehicle electrical system for > 10 seconds by
pulling the vehicle-mounted heater fuse (F1).
2. Remedy the cause of the heater interlock.
3. Connect the switched-on heater to the vehicle elec-
trical system by inserting the vehicle-mounted fuse
(F1).
4. Disconnect the switched-on heater again from the
vehicle electrical system for > 10 seconds
Heater interlock release using the DTT diagnosis:

408
Thermo H 4 Functions of the heater
ATTENTION:
It is not allowed to disconnect the heater from the
vehicle mains by pulling the heater connector under
power.
1. Read out the heater error memory using the DTT
diagnosis.
2. Disconnect the switched-on and interlocked heater
from the vehicle electrical system for > 10 seconds by
pulling the vehicle-mounted heater fuse (F1).
3. Remedy the cause of the heater interlock.
4. Reconnect the heater to the vehicle electrical system
by re-inserting the vehicle-mounted fuse (F1).
5. Clear the error memory using the DTT diagnosis.
4.3.7 Error output
If the heater is equipped with the pre-selection timer, an
error code appears on the display after a malfunction
occurs.
It is also possible to output an error via a flash code.
This is done using the operating indicator or via a lamp
connected to the two-pin plug in the heater wiring
harness.
Furthermore it is possible to output an error via the DTT
diagnosis.

501
Thermo H 5 Troubleshooting
5 Troubleshooting and error correction
5.1 General
This section describes troubleshooting and error correc-
tion for Thermo H 160, H 230, H 300 and H 350 heaters.
The safety information and regulations (see 1.6) must
be observed.
5.2 HV heater troubleshooting
The following table lists possible, general error symptoms.
Danger to life and health!
Warning!
Table 501: Error symptoms and possible causes
Error symptom Possible cause
Heater can not be switched on. • Missing or insufficient supply voltage (24V)
• 24V fuses defective or not active
• Supply lead to the plug contacts of the HV control
wiring harness (24V) defective or contact not
established
• Plug of the temperature sensors not connected
• Temperature sensors defective
• HV small distribution board defective
• HVIL (Interloop) – failure (if existent)
Temperature in the water circuit too low / too high • Control thermostat defective
• Diodes in LV wiring harness defective (if applicable,
heater may be connected incorrectly)
Heater can not be switched off. • Supply voltage (24V) not switched off
• HV small distribution board defective
• Diodes in LV wiring harness defective (if applicable,
heater may be connected incorrectly)
Heater does not heat • No HV supply connected / active
• HV fuses defective or not active
• Ground fault interrupter or insulation monitoring
device (IMD) defective or not active
• HV small distribution board defective
• Heating cartridge(s) defective