AD83.70-D-4000E | Auxiliary heater (ZHE) fault memory diagnosis | 8.10.97 |
MODELS 901.###, 902.###, 903.###, 904.### ## as of 753731 as of 3.11.97
with CODE (H12) Hot water auxiliary heater
with CODE (H86) Timer for auxiliary heater
heater designation B5WS,
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 | |
| Control unit fault | Replace control unit | |
| No start | Check fuel supply, fuel quantity and glow pin | |
| Too many attempts at starting | 5 successive start failures (see code ) | |
| flame-out | Check fuel supply and fuel quantity Check exhaust and combustion air ducts If combustion is OK, check flame sensor, replace if necessary | |
| Overvoltage | Check regulation voltage | |
| Undervoltage | Inspect fuse F9 Check battery and regulation voltage Check electrical lines (voltage drop) | |
| Premature flame detection | Check flame sensor | |
|
| Flame sensor -//- | Check flame sensor, replace if necessary | |
|
| Temperature sensor -//- | Check temperature sensor, replace if necessary | |
|
| Metering pump -//- | Inspect metering pump, replace if necessary Check electrical lines and connections | |
|
| Blower motor -//- | Check blower motor, replace if necessary | |
| Incorrect blower motor rpm | Check blower motor, replace blower if necessary | |
|
| Glow pin -//- | Check glow pin, replace if necessary Check electrical lines and connections | |
| Overheating | Temperature at temperature or overheating sensor > 125 °C Inspect coolant circuit | |
| Too many overheatings | Check temperature sensor and overheating sensor, replace if necessary Inspect coolant circuit | |
|
| Circulation pump -//- | Check electrical lines and connections, replace circulation pump if necessary | |
|
| Overheating sensor -//- | Check overheating sensor, replace if necessary | |
| Vehicle blower relay | Check connections to vehicle blower relay Check vehicle blower relay, replace if necessary |