Auxiliary heater, diagnosis, troubleshooting

AD83.70-W-5000E

Auxiliary heater, diagnosis, troubleshooting

8.12.97

Auxiliary heater (AHE) diagnosis, previous knowledge

AD83.70-W-2000D



Do not carry out measurements at contact points or plug connections with unsuitable equipment (test probes, wire ends etc.). Always use appropriate test cables from connection set (201 589 00 99 00).



Cables, plug connections and fuses are included in the following tests. The precise area of fault cause (open-circuit, short-circuit to ground, poor contact etc.) must partly be determined by further individual tests together with the currently valid wiring diagram.



If heater unit is retrofitted and a third party (e.g.drivers, customers) have made alterations / manipulations or non-specialist repairs have been made, the following test program may only be of limited use. The same applies to wiring diagram.

a

On-board voltage 22.5-29.5V

(Acid density 1.6 kg/dm3)

Troubleshooting

Complaint

Possible cause

Notes

Remedy

Auxiliary heater not functioning with

- Ignition: OFF

- Heater: ON
(button on timer with flame symbol is actuated)

No display of heat duration on timer:

Heat display lamp illuminated:

Check fuse F4 on fuse carrier A5, if in order 

AD26.45-W-6000-01A

If F4-A5 immediately trips again after being replaced 

AD83.70-W-6000-65A

AD83.70-W-6000-67A

If F6-A5 trips 

AD83.70-W-6000-60A

If F2-A5 trips 

Switch off ignition and heater unit and replace F2-A5. Switch on heater unit.

- F2-A5 trips:

Short-circuit on cable (blue/white) to TRS control unit (Z16).

- F2-A5 does not trip:

Replace Z16 on trial.

AD83.70-W-6000-69A

- Heat display lamp not illuminated with auxiliary heater: ON

- Fuse F4-A5 in order

- Auxiliary heater not functioning
(HHT does not recognize system although control unit can diagnose).



Control unit for heater unit D1L cannot diagnose.

AD26.45-W-6000-01A

- PTO indicator lamp illuminated.

- Heat display lamp not illuminated with auxiliary heater: ON

- Fuse F4-A5 in order

- Auxiliary heater not functioning

 On vehicles with electronic engine control or vehicle engine control / EDC further fault causes are possible. Look for fault according to currently valid wiring diagram (from body manufacturer if necessary).

PTO pressure switch 

AD26.45-W-6000-01A

PTO indicator lamp 

AD26.45-W-6000-02A

- Heat display illuminated with auxiliary heater: ON

- Fuse F4-A5 in order

- Auxiliary heater not functioning

- AHE system not recognized by HHT although control unit can diagnose (part no. 446)

AD83.70-W-6000-69A

Fuse F4-A5 trips immediately (on installation)

AD83.70-W-6000-67A

Fuse F4-A5 trips when auxiliary heater switched on.

AD83.70-W-6000-65A

Fuse F6-A5 trips when auxiliary heater switched on or shortly afterwards.

AD83.70-W-6000-60A

Fuse F2-A5 trips when auxiliary heater switched on or shortly afterwards.

Switch off ignition and heater unit and replace F2-A5. Switch on heater unit.

- F2-A5 trips:

Short-circuit on cable (blue/white) to TRS control unit (Z16).

- F2-A5 does not trip:

Replace Z16 on trial.

- No short run-on (approx. 20 s) takes place after heater switched off.

- Fuse F3-A5 in order

AD83.70-W-6000-70A