First check the heater air and combustion air blowers visually to determine that they are operating, then check that the fuel pump is working (the pump ticks audibly). If these units are working, check the glow-spark plug (at the same time check whether fuel is pumped into the heater - check at exhaust pipe).
Defective units should be repaired or replaced with new ones.
If this check shows that the heater is not working, check as follows:
Check all heating system units and warm air ducts as well as electrical connections for tightness, check exhaust system for damages
| Possible defect | Remedy |
|---|---|
| Reduction in exhaust pipe cross section, exhaust pipes and warm air ducts loose | Replace damaged parts with new ones |
| Loose connection in electrical system | Tighten loose push-on connections |
Check 16 Amp main fuse (no current at relay terminal E)
| Possible defect | Remedy |
|---|---|
| Short circuit in electrical system | Disconnect cables at relay terminals G, E and F. Install new fuse and reconnect cables individually. If fuse blows, check appropriate cables and units and replace if necessary. |
Check 8 Amp overheating fuse
| Possible defect | Remedy |
|---|---|
| Overheating due to failure of heater air blower | Check heater air blower |
| Warm air duct blocked (fresh air and defroster vents or outlets in footwell) | Check warm air ducts for blockage |
| Heater flaps closed | Adjust heater flap cable |
Test battery voltage
| Possible defect | Remedy |
|---|---|
| Voltage too low | Charge battery (if necessary start vehicle engine) |
Warning
Disconnect cables at fuel pump so no fuel is delivered during further tests
Disconnect cable at relay of terminal A, then reconnect cable (relay must be heard to work)
| Possible defect | Remedy |
|---|---|
| Safety switch has cut in because of defect in fuel supply or ignition system | Switch safety switch back on and eliminate defect if necessary |
| Temperature control switch defective (open circuit) | Check temperature regulating switch and temperature sensor |
| Contact on heater flap lever does not close | Check contact |
Measure voltage at relay terminals C, D and G
| Possible defect | Remedy |
|---|---|
| If there is no voltage, relay is defective (open circuit) | Install new relay |
Check whether heater air blower forces air into vehicle interior
| Possible defect | Remedy |
|---|---|
| Blower fan loose | Check heater air blower and repair or replace if necessary ( |
Disconnect cables on ignition coil and connect tachometer (Chapter 1.3), then read off speed (6400-7100 rpm at nominal voltage).
| Possible defect | Remedy |
|---|---|
| If speed too low, voltage drop in plug for combustion air blower motor or in relay | Test and install new relay if necessary |
| Armature burnt, brushes worn | Repair combustion air blower motor |
| Bearing or winding damage | Replace combustion air blower motor |
Remove 16 Amp fuse. Push heater flap lever fully forward, warning lamp goes out. Unscrew glow-spark plug. Reconnect cables, install fuse and operate heater flap lever. Sparks must jump between electrode and casing and glow element must glow.
| Possible defect | Remedy |
|---|---|
| Thermo switch defective (no current, glow time too short) | Install new thermo switch |
| Glow element open | Install new glow-spark plug |
| Glow-spark plug dirty | Clean glow-spark plug |
| Ignition contact breaker defective or maladjusted | Adjust contact breaker or replace if necessary |
| Ignition cable or coil defective | Test ignition system and install new parts if necessary |
Turn heater off, remove pump and measure capacity
| Possible defect | Remedy |
|---|---|
| Contact breaker defective or maladjusted | Adjust contact breaker or replace if necessary |
| Open circuit in pump winding | Install new pump |
| Maladjustment | Correct adjustment |
| Fuel hoses, filter or strainer blocked | Clean parts |
| Valve does not open | Replace fuel check valve. Readjust delivery capacity |