AD83.70-D-4000C | Auxiliary heater (ZHE) fault memory diagnosis | 30.6.97 |
MODELS 901.###, 902.###, 903.###, 904.### ## up to 753730 up to 31.10.97 with ENGINES 111.979, 602.980
with CODE (H12) Hot water auxiliary heater
with CODE (H86) Timer for auxiliary heater
heater designation B5WS,
heater designation D5WS
MODELS 901.###, 902.###, 903.###, 904.### ## as of 648062 up to 753730 as of 5.11.96 up to 31.10.97 with ENGINE 601.943
with CODE (H12) Hot water auxiliary heater
with CODE (H86) Timer for auxiliary heater
heater designation D5WS
Danger! | Risk of explosion caused by fuel vapors igniting, risk of poisoning caused by inhaling combustible gases and risk of injury caused by burns during and after operation of heater unit | Do not operate stationary heater, auxiliary heater or engine with heater booster in closed areas or when refueling. Allow heater unit to cool down after operation and wear protective gloves. | |
Auxiliary heater (ZHE) Diagnosis, basic knowledge | |||
I | Battery voltage > 10.5 volts | ||
II | Connecting hand-held tester (HHT) | ||
III | Remove left headlamp unit | ||
IV | complete auxiliary heater (all connectors attached) | ||
V | Ignition and auxiliary heater switched on | ||
| The cables, plugs and connectors are taken into consideration during testing with the HHT and may have to be tested again separately for discontinuity, quality of contact and correct connection in accordance with the relevant circuit diagrams | ||
Fault code | Fault text (HHT) | Possible cause / Remedy | |
| Overvoltage shutoff | Check regulation voltage | |
| Undervoltage shutoff | Inspect fuse F9. Check battery and regulation voltage. Check electrical lines (voltage drop) | |
| Overheating | Temperature at temperature or overheating sensor > 125 °C Inspect coolant circuit | |
| Possible overheating detected | Difference between temperature and overheating sensor measurements > 15 °C Check temperature sensor and overheating sensor, replace if necessary | |
| Too many overheatings | Control unit locked up because of 5th overheating in succession (see code ) | |
| Overheating detected | Temperature at temperature or overheating sensor > 130 °C Check temperature sensor and overheating sensor, replace if necessary Check coolant circuit | |
|
| Glow pin -//- | Check glow pin, replace if necessary Check electrical lines and connections | |
| Blower motor | Blower motor lockup Remedy cause of lockup, replace blower motor if necessary | |
|
| Blower motor (rpm deviation) -//- | Check connections to blower motor Check blower motor, replace if necessary | |
|
| Vehicle blower relay -//- | Check connections to vehicle blower relay Check vehicle blower relay, replace if necessary | |
|
| Circulation pump -//- | Check electrical lines and connections, replace circulation pump if necessary | |
|
| Metering pump -//- | Check electrical lines and connections Inspect metering pump, replace if necessary | |
| Too many attempts at starting | Control unit locked up because of 5 successive start failures (see code ) | |
| Cold blowing timeout | Check exhaust and combustion air ducts Check flame sensor, replace if necessary | |
| No start | Check fuel supply and fuel quantity | |
| Flame-out during operation | Check fuel supply and fuel quantity Check exhaust and combustion air ducts If combustion is OK check flame sensor, replace if necessary | |
|
| Temperature sensor -//- | Check electrical lines and connections Check temperature sensor, replace if necessary | |
|
| Flame sensor -//- | Check flame sensor connector Check flame sensor, replace if necessary | |
|
| Overheating sensor -//- | Check electrical lines and connections Check overheating sensor, replace if necessary | |
| External noise voltages | Remedy cause of noise voltages | |
| Control unit defective | Replace control unit |