Valeo Thermo G 300 Instruction manual

Rev. 12/2018
Id.No. DOK50036
Thermo G 300
with control unit 1588
Workshop Manual
HEATING SYSTEMS

Thermo G Content
1
1 Introduction 101
1.1 Content and purpose 101
1.2 Meaning of warnings and highlighted content 101
1.3 Further documentation to be used 101
1.4 Safety information and regulations 101
1.4.1 General safety regulations 101
1.4.2 Other safety information 102
1.5 Suggestions for Improvement and change 102
2 Technical data 201
2.1 Heater 201
2.1.1 Altitude capability 201
2.2 Gas pressure regulator 202
2.3 Fuel 202
2.4 Circulating pump 202
3 Description of assemblies and components 301
3.1 Burner head 302
3.1.1 Combustion air fan 302
3.1.2 Control device 302
3.1.3 Mixing chamber 302
3.1.4 Heat protection cover 303
3.1.5 ZF Module with electronic ignition unit and ionization electrode 303
3.1.6 Flame tube 303
3.2 Combustion chamber 303
3.3 Heat exchanger 303
3.4 Temperature sensors with water temperature sensor and integrated overheating protection 304
3.5 Gas pressure regulator 305
3.5.1 Heating of the gas pressure regulator 305
3.6 Circulating pump 305
4 Heater functions 401
4.1 General heater functionality description 401
4.2 Operational heater sequence 402
4.2.1 Switching on and start 402
4.2.2 Heating operation 402
4.2.3 Switching off 403
4.3 Malfunction interlock and heater interlock 404
4.4 Malfunction interlock 404
4.4.1 Malfunctions during switching-on and start procedure 404
4.4.2 Malfunctions during heater operation 404
4.4.3 Malfunctions during purge cycle 404
4.4.4 Malfunction interlock release and error clearance 405
4.5 Heater interlock 405
4.5.1 Heater interlock release 405
4.6 Error output 405
5 Troubleshooting 501
5.1 General 501
5.2 General error symptoms 501
5.3 Malfunction code output via flash code 503
5.4 Error symptoms during functional tests with malfunction code output 505
5.4.1 Error symptom "No start within safety period" 505
5.4.2 Error symptom "Flame interruption" 505

Thermo G Content
2
5.4.3 Error symptom "Low voltage" 507
5.4.4 Error symptom "Extraneous light detected prior to ignition or during purge cycle" 508
5.4.5 Error symptoms "Temperature sensor / overheating protection defective" 509
5.4.6 Error symptom "Solenoid valve 1 or 2 defective" 509
5.4.7 Error symptom "Overheat protection has triggered" 510
5.5 Individual component tests 511
5.5.1 General visual inspection 511
5.5.2 Heat exchanger visual inspection 511
5.5.3 Visual inspection of exhaust outlet and exhaust line 511
5.5.4 Combustion chamber visual inspection 511
5.5.5 Resistance check of the temperature sensor with integrated overheat protection 511
5.5.6 Fan and combustion air intake line visual inspection 512
5.5.7 Burner motor inspection 512
5.5.8 ZF module inspection 512
5.5.9 Ignition electrode inspection 513
5.5.10 Heat protection cover inspection 514
5.5.11 Gas pressure regulator inspection 514
6 Wiring diagrams 601
6.1 General 601
7 Servicing 701
7.1 General 701
7.2 Heater Servicing 701
7.3 Vehicle Servicing 701
7.4 Heater test run 701
7.5 Servicing 701
7.6 Measurement and adjustment of the exhaust CO2 content 702
7.6.1 Measurement of the exhaust CO2 content 702
7.6.2 Adjustment of the exhaust CO2 content 702
8 Removal and installation of components and of the heater 801
8.1 General 801
8.2 Removal and installation of the temperature sensor with integrated overheating protection 801
8.3 Hood removal and installation 802
8.4 Burner head Removal and installation 802
8.5 Separating the fan housing from the mixing chamber 803
8.6 Control device removal and Installation 804
8.7 Fan wheel removal and installation 804
8.8 Fan motor removal and installation 804
8.9 ZF module removal and installation 804
8.10 Combustion chamber removal and installation 806
8.11 Heat exchanger removal and installation 806
8.12 Heater removal and installation 807
8.13 Gas pressure regulator removal and installation 807
8.14 Start-up after installation of burner head, heater or heat exchanger 807
8.14.1 Bleeding of the coolant circuit 807
9 Modifications and retrofits 901

Thermo G Content
3
10 Packing / storage and shipping 1001
10.1 General 1001
Appendix
Scheduled heater maintenance A-1

101
Thermo G 1 Introduction
1Introduction
1.1 Content and purpose
This workshop manual is intended for the maintenance
and repair of the water heaters (hereinafter heaters)
Thermo G300 on the gas low pressure side.
Work on the heater must only be carried out by
trained and / or by Valeo-trained personnel.
Any work on the gas supply line, for example when
removing or installing the gas regulator, may only be
carried out by persons with the appropriate official
authorization.
1.2 Meaning of warnings and 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.
1.3 Further documentation to be used
In the Thermo G Operating and Service Instructions
you will find all the necessary information as well as useful
hints relating to the safe operation of the heater.
The Thermo G Installation Instructions contain all
required information as well as useful hints for the correct
installation of the heater.
Spare parts required during maintenance and repair, you
can order using the Thermo G Spare Parts List at Valeo.
If necessary, Valeo will publish Technical Information
(TI) for operation, maintenance or repair of the heater.
The Heater Accessories Catalog contains useful acces-
sories for your heater installation.
All mentioned documents you will find on the Valeo
website www.valeo-thermalbus.com/eu_de/Service.
1.4 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 in the individual sections or procedures with
headings in capital letters.
1.4.1 General safety regulations
Read the Thermo G Operating and Service Instruc-
tions before operating the heater for first time.
Familiarize yourself with the Thermo G Installation
Instructions before you make any modifications to the
existing heater installation.
NOTE:
The Thermo G Operating and Service Instructions contain
safety instructions and regulations to be followed for safe
operation of the heater.
The Thermo G Installation Instructions contain the
statutory regulations and other safety hints and regula-
tions for the proper installation of the heater.
Danger to life and health!
Warning!
Danger to life and health!
Warning!
Hazardous to health!
Caution!
Danger to life and health!
Warning!

102
Thermo G 1 Introduction
1.4.2 Other safety information
1.4.2.1 Temperature sensor
ATTENTION:
The temperature sensor cable may not be mechani-
cally stressed (pull on the cable, carry the heater at
the cable etc.).
1.5 Suggestions for Improvement and
change
Please direct any complaints, improvement or modifica-
tion suggestions regarding this manual to:
service-va[email protected]om
STOP!

201
Thermo G 2 Technical data
2 Technical data
Unless limiting values are defined, the technical data
should be understood with tolerances of ±10% common
for heaters at an ambient temperature of +20°C, and at
nominal voltage.
2.1 Heater
2.1.1 Altitude capability
The heater is adjusted in the factory, and without change
of the CO2adjustment unlimited usable up to an altitude
of 1500 m above MSL, above an altitude of 1500 m up to
2000 m an application with splash guard or combustion air
intake line must be used.
Table 201 Technical data heater
Heater
ECE type approval number E1 122R-00 0447 / E1 10R-04 7263
Kind of design Low-pressure gas burner
Heat output 30 kW ±10%
Fuel CNG (natural gas) classes H/L
Combustion gas pressure when it enters the heater -2.5 mbar
Fuel cosumption at CNG class H < 2.95 kg/h
Rated voltage 24 Volt
Operating voltage range 20.5 ... 30 Volt
Rated power consumption without circulating pump 110 W
Current in standby mode < 1 mA
Max. current at the circulating pump output 12A
Used gas pressure regulator M96-E-SP
Max. ambient temperature for the heater and control device Storage temperature -40 ... +120°C
Operating temperature -40 ... +100°C
Permissible sucked in combustion air temp. (permanent) -40 ... +60°C
Permissible operating overpressure 2.0 bar
Capacity of the heat exchanger 1.8 l
Minimum capacity of the water system 25.00 l
Minimum water flow 2400 l/h
CO2in exhaust gas at rated voltage 8.0 ... 9.0 Vol.-%
Switch thresholds switches off at 82°C ±1K
switches on at 72°C ±1K
Heater dimensions
(tolerance ±3 mm)
L 585 mm
W 247 mm
H 226 mm
Heater weight 19 kg

202
Thermo G 2 Technical data
2.2 Gas pressure regulator
Table 202 Technical data gas pressure regulator
2.3 Fuel
ATTENTION:
The heater may only be operated using natural gas
(CNG).
As fuel natural gas (CNG) with a minimum methane
content of 95 % is used.
If natural gas with a less methane content is used (natural
gas of class L), the CO2level must be adjusted according
to section 7.6.2 in chapter 7.
The max. oil content of the gas is 10 mg/m3.
2.4 Circulating pump
All desired information about the Valeo circulation pumps
can be found under www.valeo-thermalbus.com/eu_en/
Products/Pumps.
Gas pressure regulator
Test certificate ECE R110, R10.04
Kind of gas Natural gas (CNG) class H/L
Permissible oil content in gas < 10 mg/m³
Input pressure 5 ... 220 bar
Output pressure -0.25 ... -2.5 mbar
Pressure 1st stage 1.8 ... 3.5 bar
Pressure 2nd stage 0.65 ... 0.75 bar
Operating temperature -40 ... +120°C
Sorage temperature -40 ... +100°C
Rated voltage 24 V
Nominal coil power at rated voltage (2x) 24 W
Operating voltage range 20 ... 30 V
Dimensions
(tolerance ±3 mm)
L 150 mm
W 130 mm
H 170 mm
Weight 1.7 kg

301
Thermo G 3 Description of assemblies and components
3 Description of assemblies and
components
The water heater Thermo G 300 operates in conjunction
with the on-board heating system
– to heat the passenger compartment
– to defrost the windscreen, and
– to pre-heat the water-cooled engines
in busses.
The water heater operates independently of the vehicle’s
engine and is connected to the cooling system, the gas
system and the electrical system of the vehicle. It is
screw-mounted to the chassis of the vehicle or an addi-
tional crossmember.
The heat is generated by the combustion of the gas. Via
the heat exchanger of the heater, the heat is dissipated to
a coolant circuit. The adaptation to the changing demand
of heat is reached by intermittent operation.
An integrated control device controls on the basis of the
signals of a temperature sensor the on and off switching
of the burner.
The heater Thermo G basically consists of:
– the burner head
– the combustion chamber
– the heat exchanger
– temperature sensor system
In addition, a circulating pump and a gas pressure regu-
lator for the gas supply to the heater are installed in the
vehicle.
1 Combustion air, intake
2 Hood
3 Fan housing
4 Coolant, inlet
5 Temperature sensor with integrated
overheat protection
6 Coolant, outlet
7 Heat exchanger
8 Plug, sensor system
9 Exhaust outlet
10 Control device
11 Gas port
12 Mesh
13 Protective grid
1
2
3
45
6
8
9
7
10
11
12
13

302
Thermo G 3 Description of assemblies and components
3.1 Burner head
The burner head consists of the components
• combustion air fan
• control device
• mixing chamber
• heat protection cover
• ZF module with electronic ignition unit and ionization
electrode
•flametube
3.1.1 Combustion air fan
The combustion air fan transports the air required for
combustion from the combustion air intake to the combus-
tion chamber.
By the air fan in addition, the required amount of gas is
sucked in through the gas pressure regulator.
The air fan consists of the combustion air motor and the
fan wheel. Air is sucked in through a protective grid in the
hood and mixed with the gas in the mixing chamber.
If an air intake extension is used the combustion air is
sucked in through this extension.
3.1.2 Control device
The control unit 1588 ensures the operating sequence
and monitors the burner operation.
3.1.3 Mixing chamber
In the mixing chamber, the gas is mixed with the combus-
tion air and then guided into the flame tube.
Across the surface of the mixing chamber evenly small
bulges are distributed. On the one hand they generate
turbulence for mixing of gas and combustion air and on
the other hand they increase the flow-around surface of
the mixing chamber. So it is cooled more effectively.
Circlip
Fan wheel
Motor
Control device 1588
Socket P
customer
connector
Socket P
Socket T
diagnostic system
Socket D
Socket V
solenoid valves
and electrical circulating pump
temperature sensor system
regulator heating

303
Thermo G 3 Description of assemblies and components
3.1.4 Heat protection cover
The heat protection cover is glued to the mixing chamber.
3.1.5 ZF Module with electronic ignition unit
and ionization electrode
The electronic ignition unit induces the high voltage
required for ignition of the gas-air mixture. Ignition is
triggered by a high voltage spark between the two ignition
electrodes.
The ZF module is used simultaneously for monitoring the
flame in the combustion chamber. In principle it is an
ionization flame guard.
As ionization electrode one of the two ignition electrodes
of the ZF module is used. The counter-electrode is the
flame tube, which is connected over a ground terminal to
the housing with the control device.
The burning flame establishes an electrically conductive
connection from the ionization electrode to the flame tube,
and so to the ground potential. This ionization current is
measured in the control device. Thereby, the presence or
absence of a flame can be clearly detected.
The flame monitoring is part of the control.
3.1.6 Flame tube
The flame tube ensures a defined, homogeneous flame
ring in the combustion chamber.
For that, a plurality of outlet openings for the gas-air
mixture across its surface are distributed in a defined
pattern. Each opening acts like a nozzle.
3.2 Combustion chamber
In the combustion chamber the gas-air mixture is burned.
It ensures that the generated during combustion hot
exhaust gases are directed through the fins of the heat
exchanger.
3.3 Heat exchanger
In the heat exchanger, the heat produced by the combus-
tion is transferred to the coolant circuit.
Inside it has circularly arranged fins through which the hot
exhaust gases generated during combustion are led.
In the outer shell flows the water of the coolant circuit
through. There are two welded-on connection pieces, one
for the coolant inlet and one for the coolant outlet.
Heat protection cover
Ignition
Ionization electrode
ZF Module
electrodes
Coolant inlet
Coolant outlet
Exhaust outlet

304
Thermo G 3 Description of assemblies and components
3.4 Temperature sensors with water
temperature sensor and integrated
overheating protection
The water temperature sensor captures the coolant
temperature at the heat exchanger outlet as electrical
resistance.
This signal is transmitted to the control unit, where it is
processed.
The overheating protection integrated into the tempera-
ture sensor is responsible for temperature limitation.
Similar to the water temperature sensor, the coolant
temperature is captured at the heat exchanger outlet as
electrical resistance and transmitted to the control unit.
Overheating protection prevents inadmissibly high heater
operating temperatures.
At a temperature greater than 135°C heater deactivation
and interlocking is initiated.
It is not necessary to manually reset the overheating
protection.
Connector
Temperature sensor
incl. overheat protection

305
Thermo G 3 Description of assemblies and components
3.5 Gas pressure regulator
Gas is supplied by means of the vehicle’s gas supply sy-
stem, in which the gas pressure regulator is incorporated.
The gas pressure regulator regulates the storage pres-
sure (max. 220 / min. 5 bar) downward in 3 steps to the
required operating pressure. In the regulator at a pressure
below atmospheric pressure the required quantity of gas
is released by a diaphragm valve.
The gas pressure regulator has two solenoid valves (see
Fig. below).
Solenoid 1 (MV1) opens the gas supply from the storage
tank to the gas pressure regulator (high pressure branch).
Solenoid 2 (MV2) opens the gas supply from the gas pres-
sure regulator to the heater (low pressure branch).
Both solenoid valves are controlled by the control device.
Thus, the gas pressure regulator is integrated into the
control concept of the heater.
.
3.5.1 Heating of the gas pressure regulator
As the expansion of the compressed gas causes conside-
rable cooling, the gas pressure regulator must be warmed
up. This is accomplished by its integration into the cool
water circuit.
By means of T-pieces the gas pressure regulator is
connected with the water outlet and the water inlet at the
heater.
Heated water is branched off at the water outlet and flows
through the gas regulator. Then it re-enters the heater
through the water inlet.
The gas regulator further has an electrical preheating
(ERH). The heating cartridge is connected to a dedicated
output on the control unit.
The ERH is activated at (water) temperatures below -20°C
by the control unit. It is switched off again at a water
temperature above -10°C. In addition, the initial cycle time
from regularly 15 seconds increases to 40 seconds in
water temperatures below -20°C.
3.6 Circulating pump
The externally arranged circulating pump ensures coolant
transport within the vehicle and/or heater circulation
system.
Depending on the application, the circulating pump is swit-
ched on via the control unit or directly via the vehicle
electrical system and operated during the entire heater
operation duration.
Further information on installation and operation of the
circulating pump contain the Thermo G Installation
instructions.
All service information regarding your Valeo circulating
pump(s) can be found under www.valeo-thermalbus.com/
eu_en/Products/Pumps.
High pressure
solenoid valve
(MV1)
Low pressure
solenoid valve
(MV2)
Gas outlet
Gas inlet
Water outlet
Water inlet
Screw for fixation
of the heating cartridge

401
Thermo G 4 Heater functions
4 Heater functions
4.1 General heater functionality
description
The heater function is based on the principle of the low-
pressure gas burner and is controlled by a micro
processor. At the same time the integrated control unit
takes over all monitoring functions.
An electronically controlled motor drives a fan which
sucks in combustion air and gas as fuel. Both are mixed
in a mixing chamber. The gas-air mixture is then fed into
the combustion chamber of the heater and burned there.
The hot exhaust gases flow through a heat exchanger and
thus provide heat to the water circuit connected to the
heater.
The heater works intermittently, that means the gas
burner is switched on and off according to the heat
demand in the water cycle.
The ignition of the gas-air mixture takes place in the
combustion chamber by high-voltage ignition sparks.
The flame recognition is carried out by an in the ZF-
module (electronic ignition unit) integrated flame guard.
The principle is based on the measurement of the ionisa-
tion current through the flame.
Depending on the equipment, the heater is switched on
and off using a
• digital timer
•switch
• or climate control.
During heating operation the burner is automatically swit-
ched on and off. For regulation a temperature sensor is
installed in the coolant outlet of the heat exchanger. The
heater is switched on, when the temperature falls short of
a lower temperature threshold (72°C), and is switched off,
if the upper temperature threshold is reached (82°C). A
distinction between parking heating and auxiliary heating
mode does not exists.
For overheating protection of the heater the switching
thresholds are modified by the control unit, if specified
temperature gradients are exceeded (gradient evalua-
tion).
An operating display is available for monitoring the opera-
ting status. The operating display is also used to output
error messages in flash code.

402
Thermo G 4 Heater functions
4.2 Operational heater sequence
4.2.1 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. This takes approx.
15 seconds, if the coolant temperature is below -20°C
approx. 40 seconds.
The initial cycle is used to start the combustion air motor
and to query the flame monitoring. By the combustion air
motor, the heat exchanger is flushed and at the same time
a negative pressure to the gas pressure regulator is
generated.
The solenoid valve 1 at the gas pressure regulator is swit-
ched on (open), so that the gas can flow from the gas tank
into the gas pressure regulator.
Then, during the pre-ignition the electronic ignition unit is
turned on to check its function, and to ensure an imme-
diate ignition when the gas flows in.
Approximately 1 second later the solenoid valve 2 at the
gas pressure regulator is turned on (open) and now gas
can sucked in.
With the opening of the solenoid valve 2, the safety time
begins (10 s).
When the gas-air mixture the combustion chamber has
reached, it is ignited by the activated electronic ignition
unit.
When the ignition of the gas-air mixture was successful,
the flame guard detects the flame, and the system state
will change to flame stabilization.
The state flame stabilization is used to stabilize the
combustion and ends with the query / decision of the
flame guard "flame". If yes, the system changes into the
heating mode.
NOTE:
If during the start the main switch is turned off, or the water
temperature rises above the upper temperature threshold,
or a fault is detected, the system switches into the purge
cycle.
4.2.2 Heating operation
After the flame is stabilized, the heater is in controlled
operation.
The operation indication, the circulating pump, the
combustion air motor, the solenoid valves 1 and 2 at the
gas pressure regulator and the flame guard are active.
Once the upper switching threshold is exceeded, the
heating operation is terminated and the purge cycle is
initiated. The solenoid valves at the gas pressure regu-
lator are closed, the flame extinguishes, but the combus-
tion air fan and the circulating pump continue running.
Fig. 401 Operational sequence
* Coolant temperature below -20°C 40 seconds, otherwise 15 seconds, plus 0.3 seconds delayed switching of the combustion air motor and circulating pump
** On/Off depending on T
Process
Signals
Main switch off on off
Coolant temperature T > T_min T < T_min T >= T_max T < T_min T >= T_max T < T_min
Flame
generation
Flame
generation
Flame
generation
Actuators
Operating display
Combustion air motor
Circulating pump
Electronic ignition unit
Solenoid valve 1
Solenoid valve 2
ERH **
Time in s 3 37/12* 1 9 1 ... 5 115 3 37/12* 1 9 1 ... 5 115 12 37/12* 1 9 1 ... 5 115
State
Ready to start Initial cycle with light check Pre-ignition Ignition Stabilization Purge cycle 1 with safety period Purge cycle 2 Initial cycle with light check Pre-ignition Ignition Stabilization Purge cycle 1 with safety period Purge cycle 2 Initial cycle with light check Pre-ignition Ignition Stabilization Purge cycle 1 with safety period Purge cycle 2
Off Standby Start Heating
Purge
cycle Standby Start Heating
Purge
cycle Standby Start Heating
Purge
cycle Off

403
Thermo G 4 Heater functions
After a safety period of 5 seconds the purge cycle 2 starts.
The flame monitoring is evaluated.
The purge cycle ends approx. after 115 seconds. The
combustion air fan is switched off.
The heater is in a controlled break.
The operation indication, the flame guard and the circula-
ting pump continue their operation.
NOTE:
If during the purge cycle 2 a “flame“ is recognized, the
combustion air motor is switched off and an appropriate
error message is given.
The operation indication, the flame guard and the circula-
ting pump continue to run until the purge cycle 2 is
terminated (after 115 seconds).
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
sequence.
4.2.2.1 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 thres-
hold to a lower value.
The quicker the temperature increases, the lower the swit-
ching 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.
If the temperature rise (temperature gradient) is again
within permissible limits, the thresholds are reset to
normal values immediately (lower threshold 72°C, upper
threshold 82°C).
4.2.3 Switching off
Switching the heater off ends the combustion process.
The operation indication goes off and the purge cycle is
initiated.
The purge cycle cools down the components. This
prevents that the residual heat in the heat exchanger,
which is still present, overheats the components.
The solenoid valves 1 and 2 at the gas pressure regulator
are closed, the flame extinguishes, combustion air fan and
the circulating pump continue running.
After a safety period of 5 seconds the purge cycle 2 starts.
The flame monitoring is evaluated.
The purge cycle ends approx. after 115 seconds. The
combustion air fan, the flame guard and the circulating
pump are switched off.

404
Thermo G 4 Heater functions
4.3 Malfunction interlock and heater
interlock
Malfunction interlocks and heater interlocks are distin-
guished.
The interlocks protect the heater and the surrounding
vehicle assemblies against sequence errors after failure
or malfunction of individual heater components.
In a heater interlock safety-related components are
affected by the failure or malfunction. It may only be
released by Valeo-trained personnel after eliminating the
cause.
4.4 Malfunction interlock
If one of the malfunctions listed below occurs, the heater
will initiate a fault shut-down, followed by malfunction
interlock.
In the process a purge cycle up to 115 seconds duration
can be executed.
An error code is outputted by means of flash impulses via
the operating display.
In case of several sequential malfunction interlocks a
heater interlock is initiated (see 4.5).
4.4.1 Malfunctions during switching-on and
start procedure
Malfunction causes:
• Short circuit and/or interruption of electrical compo-
nents (temperature sensor, combustion air motor,
circulating pump, solenoid valves 1 and 2, electronic
ignition unit of the ZF module, electrical regulator
heating)
• Flame detection during intial cycle
• No start: No flame detection within 10 seconds after
opening of the solenoid valve 2
• Heater operation outside the permissible operation
temperature range.
• Voltage falling short of the low voltage threshold of
approx. 20.5 V within a duration of 20 seconds after a
heating request.
• Voltage exceeding the high voltage threshold of
approx. 30 V within a duration of 6 seconds after a
heating request (purge cycle only and after that the
heater goes into the standby mode, no malfunction
interlock).
NOTE:
As soon as the overvoltage is eliminated (6 seconds conti-
nuously), the heater restarts operation automatically
according to functional sequence.
4.4.2 Malfunctions during heater operation
Malfunction causes:
• Short circuit and/or interruption of electrical compo-
nents (temperature sensor, combustion air motor,
circulating pump, solenoid valves 1 and 2, electronic
ignition unit of the ZF module, electrical regulator
heating)
• Heater operation outside the permissible operation
temperature range.
• Flame interruption (more than 5 consecutive combus-
tion faults by a flameout)
NOTE:
After a combustion fault by a flameout the heater is swit-
ched into the state „flushing“.
In this case, the gas supply is interrupted by the solenoid
valve 2 at the gas pressure regulator, the combustion air
motor continues to run.
If a component test has shown no errors and no flame is
detected by the flame guard, after 10 seconds the pre-
ignition is performed for the resumption of the combustion
operation as during the normal start.
• Voltage falling short of the low voltage threshold of
approx. 20.5 V within a duration of 20 seconds
• Voltage exceeding the high voltage threshold of
approx. 30 V within a duration of 6 seconds (it takes
place a purge cycle only, and after that the heater
goes into the standby mode, no malfunction interlock)
NOTE:
As soon as the overvoltage is eliminated (6 seconds conti-
nuously), the heater restarts operation automatically
according to functional sequence.
4.4.3 Malfunctions during purge cycle
Malfunction causes:
• Short circuit and/or interruption of electrical compo-
nents (temperature sensor, combustion air motor,
circulating pump, solenoid valves 1 and 2, electronic
ignition unit of the ZF module, electrical regulator
heating)
• Heater operation outside the permissible operation
temperature range.
• Voltage falling short of the low voltage threshold of
approx. 20.5 V within a duration of 20 seconds
• Voltage exceeding the high voltage threshold of
approx. 30 V within a duration of 6 seconds (it takes
place a purge cycle only, and after that the heater
goes into the standby mode, no malfunction interlock)
NOTE:
As soon as the overvoltage is eliminated (6 seconds conti-
nuously), the heater restarts operation automatically
according to functional sequence.

405
Thermo G 4 Heater functions
4.4.4 Malfunction interlock release and error
clearance
The malfunction interlock is released when the heater is
switched off.
After that it will be immediately ready for operation.
Resetting a malfunction interlock leads to:
• Clear the lock of the outputs with errors, that means
the outputs are activated again, an error can be
detected again.
• The blink code output is reset, it will return to the
output of the main switch state via the operation
display.
• The fault counter status for the / fault is reset, that
means, the fault counter can be increased for any
errors again.
4.5 Heater interlock
The heater interlock overrides the standard malfunc-
tion interlock.
If the heater interlock is active, neither start nor purge
cycle are executed after the heater is switched on again.
Prior to restarting the heater, cause investigation and trou-
bleshooting must be performed by Valeo-trained
personnel.
After that the heater interlock can be released (see 4.5.1).
Heater interlock causes:
• Short circuit and/or interruption of the temperature
sensor, overheat protection, solenoid valve 2
• Flame guard defective
• Overheat protection triggered
• Flame detection after „flushing“
• Flame detection during the purge cycle 2
• Control device fault or programming error
• Repeated malfunctions (8)
• Repeated flame interruptions (5)
4.5.1 Heater interlock release
ATTENTION:
Prior to releasing the heater interlock the cause of the
fault must be eliminated!
The heater interlock release is permitted by Valeo-
trained personnel only.
To release the heater interlock, the heater must be
disconnected from the vehicle electrical system when it is
on.
The heater interlock release is performed using the follo-
wing sequence:
1. Correct the cause of the heater interlock.
2. Switch interlocked heater on.
3. Disconnect the switched on heater for > 10 seconds
from the vehicle electrical system.
4. Reconnect the switched on heater to the vehicle
electrical system.
NOTE:
The heater automatically starts after connecting it to
the vehicle electrical system.
The heater can be switched off during the initial cycle.
The heater interlock release additionally leads to:
• Reset of the fault counter to 0
• Reset of the flame interruption counter to 0
• Reset of the start interruption counter to 0
The heater interlock is recorded by the control device.
4.6 Error output
If the heater is equipped with the standard timer, an error
code is displayed on the digital timer after a malfunction
occurs, otherwise via flash code given by the operating
indicator light.

501
Thermo G 5 Troubleshooting
5 Troubleshooting
5.1 General
This section describes the troubleshooting at the heater
Thermo G 300.
ATTENTION:
Troubleshooting may only be performed by briefed and
competent trained personnel.
In case of doubt functional relations can be obtained in
chapters 3 and 4.
Error recognition is usually limited to localizing the faulty
component.
The following malfunction causes are not taken into consi-
deration and should basically always be verified and/or a
malfunction due to these reasons should be excluded:
• Corrosion on plugs
• Loose plug connections
• Crimp failures on plugs and/or pins
• Corrosion on cable and fuses
• Corrosion on battery terminals
• Cable insulation damage
ATTENTION:
Prior to replacing a fuse troubleshooting needs to be
performed. The heater must be disconnected from the
vehicle electrical system and the fuse is to be replaced
when the heater is in currentless state.
A properly dimensioned fuse must be inserted (see
chapter 6 Schematic diagrams).
After each error correction a functional test must be
performed in the vehicle.
5.2 General error symptoms
The following table lists the possible, general error symp-
toms.
Table 503 General error symptoms
Error symptom Possible cause
Error in the electrics
Operating indication is not illuminated and the heater
does not function.
• No voltage supply
• Fuse(s) defective
• Cable to the pins of plug C of the control device
Fuse F1 triggered Short circuit or overload of cables and/or heater
components
Check cables, connectors and components and replace
as required.
Fuse F2 triggered. Short circuit or overload of cables or of the circulating
pump
Check cables, connectors and components and replace
as required.
Fuse F3 triggered Short circuit in the supply cable to the main switch or, if
installed, in the digital timer
Heater is functional, however the operating display is not
illuminated
Operating indication defective or cables leading to the
operating indication interrupted or shorted

502
Thermo G 5 Troubleshooting
Fehler im Wassersystem
Circulating pump failure ( Aquavent 6000S and Aquavent
6000SC only).
• Error mode activated
In case of malfunctions the motor is switched off via the
error mode
Reactivation of the circulating pump motor
For this purpose disconnect the power supply for > 2 min.
After the power supply is reconnected the motor
performs a soft start.
Heater stops as the connected heat exchanger provides
insufficient heat.
Flow rate too small, because
• Air in the heater, heat exchanger or in system
sections
• Taps/valves (flow controllers) throttled,
contaminated, closed.
• Contaminations in the system, e.g. filters or at bottle
necks
• Circulating pump delivery rate insufficient(air in
pump housing)
• insufficient frost protection (antifreeze)
• System resistance too high (especially high in cold
weather)
• Circulating pump defective
Heat exchanger provides not enough heat, because
• Air in the heat exchangers and/or system sections
• Contaminated heat exchangers
• Insufficient air entry or air exit
• Fan: Insufficient delivery rate / incorrect direction of
rotation / resistance too high
• Antifreeze content too high
Approximate flow rate determination:
Heat flow [kW] according to type plate
Flow rate in in [l/h] = x 860
Temperature difference ∆t in [K]
measured on the heater between water inlet and water outlet
(e.g. using contact thermometer)
Table 503 General error symptoms
Error symptom Possible cause