Webasto Thermo Pro 90 Series Service Installations page 20

5 Malfunctions and troubleshooting
Symptom
C Excessive smoke from
heater during start-up
phase
Heater goes out prema-
D turely
E Irregular
combustion noise
506
Possible cause Corrective measures
Glow plug –
–
DP42 fuel pump See symptom B, DP42 fuel pump
Combustion air fan See symptom B, combustion air fan
Fuel integration –
–
–
–
–
Exhaust system and air –
intake system –
–
–
–
Burner unit –
–
Undervoltage detection –
–
–
DP42 fuel pump See symptom B, DP42 fuel pump
Combustion air fan See symptom B, combustion air fan
moves stiffly
Fuel integration See symptom C, fuel integration
Coolant circuit –
–
–
–
Exhaust system and air See symptom C, exhaust system and air intake system
intake system
Burner unit See symptom C, burner unit
DP42 fuel pump See symptom B, DP42 fuel pump
Burner unit See symptom C, burner unit
Connect Webasto Thermo Test and evaluate.
Measure glow plug resistance at glow plug connector X2, see Section
6.4.2. Measured values: (cold resistance at 25 °C):
• 0.235 to 0.305 ohm, 12 V version
• 0.670 to 0.870 ohm, 24 V version (green mark on glow plug)
Check fuel level and fuel take-off from fuel tank
Check integration in the vehicle's fuel system
Check fuel lines for leaks, kinks and clogging, especially in the area of
line connectors on the intake side
Disconnect fuel line from heater, hold hose in a collection container
and operate the fuel pump with Webasto Thermo Test PC
Diagnostics. (Measured fuel delivery rate 115 ml/h*Hz) Fuel should be
free of bubbles
The fuel pipe of the burner unit is clogged if fuel flows out of the line
when it is disconnected from the heater, replace burner unit
Check that the lines are not clogged
Rectify any leaks in the intake line and exhaust pipe (no CO
air)
Exhaust pipe outlet is not located under the intake line inlet.
Check that intake line and exhaust pipe are installed in accordance
with installation instructions
Check that there is sufficient distance from the interior fresh air intake
to the vehicle
Removal and visual inspection
Replace the burner unit if the fuel pipe is clogged
Check fuses (F2, F3)
Webasto Thermo Test PC Diagnostics, check supply voltage
Without Webasto Thermo Test: measure supply voltage at heater
connector X8, Pin 12 (see Fig. 1112). Setpoints:
• 12 V version:
The voltage must not drop below 10.5 V for more than 10 s
• 24 V version:
The voltage must not drop below 20.0 V for more than 10 s
Check integration in vehicle's coolant circuit in accordance with
general installation instructions. Remove kinks and chafing points.
Check heater, water connection, coolant pump and hoses for leaks,
rectifying if necessary
Check that coolant circuit is bled correctly
Check circulation in coolant circuit
Thermo Pro 90
in intake
2