AD83.70-W-5000C | Auxiliary heater, diagnosis, troubleshooting | 3.12.97 |
MODEL 625.1 /2, 655, 656, 657, 658, 659 with CODE (H27) Hot water auxiliary heater DW 80
MODEL 650, 651, 652, 653, 654 with CODE (H27) Hot water auxiliary heater DW 80
Danger! | Risk of explosion due to fuel vapors, risk of poisoning from combustion gases and risk of injury from burning during or after heater operation | Do not put stationary heater, auxiliary heater or engine with heater booster into operation in confined spaces or when filling fuel tank. Allow heater unit to cool down after operation and wear protective gloves. | |
Danger! | Risk of injury to skin and eyes through scalding by hot, pressurized coolant. Risk of poisoning through swallowing coolant. | Open cooling system only when coolant temperature is below 90°C. Slowly unscrew cap and allow the excess pressure to escape. Coolant should not be poured into drinking vessels. Wear protective gloves, protective clothing and protective glasses. | |
Auxiliary heater (AHE) diagnosis, previous knowledge | |||
a | Vehicle voltage 22.5-29.5V (Acid density >1.16) | ||
Troubleshooting | |||
Complaint | Possible cause | Notes | Remedy / test step |
Auxiliary heater does not run with ignition OFF | Defective fuse | Operating display of timer not illuminated. Operating display of timer illuminated. (Fuse F1 and cab lamp in order) | Check fuse (F1/A1). - If fuse not in order: - If fuse trips again: Short-circuit to ground at cab / entry lamp, supply cable to cab / entry lamp, supply cable to timer or in timer. Check fuse (F6/A5). - If fuse in order: - If fuse trips again: Short-circuit to ground at supply cable to control unit or on/in control unit. |
Operating display illuminated with ignition OFF after heater switched on, but heater not functioning. | Cable open-circuit | ||
Fuse F6/A5 trips with ignition OFF after auxiliary heater switched on or shortly after (plug A on control unit disconnected) | Short-circuit to ground in/on control unit | ||
No display (time) on heater display with ignition OFF. Auxiliary heater runs with ignition ON for no longer than 30 or 60 minutes (depending upon installed timer). Auxiliary heater may run longer than 5 minutes with ignition switched off. | Check fuse (F7/A5). - If fuse in order: - If fuse trips again: Short-circuit to ground on supply cable to timer, possibly in timer. Short-circuit to ground / short-circuit in coil on solenoid valve (Y61, coolant circulation) or on its supply cable. Short-circuit to ground on supply cable to air circulation flap adjustment, possible on air circulation flap adjustment switch or on/in air circulation flap motor. Short-circuit to ground on supply cable to battery master switch on vehicles with battery master switch. |
Referenced documents
- ad8370w2000c Auxiliary heater (AHE) diagnosis previous knowledge
- ad8370w600039a AHE test of electrical system timer supply voltage
- ad8370w600040a AHE test of electrical system timer
- ad8370w600042a AHE test of electrical system control unit output glow pin
- ad8370w600044a AHE test of electrical system timer output fuse carrier
- as2000z000101a Risk of injury to skin and eyes suffering scalding from contact with hot coolantspray. Risk of poisoning from swallowing coolant.
- as8370z000201a 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