Important Notes For Fault Diagnosis

The electronics and software used to automatically control the temperature in the cabin have been developed and modified through the years. This means that fault diagnosis also varies between year models.

In cars of year model 1985-89, the electronics are somewhat simpler, meaning that fault diagnosis is also simpler.

Between 1990-94, the ISAT scan tool is used, making it possible to enter commands and read values during fault diagnosis.

When rear A/C was introduced as an option in 1992, diagnostic trouble codes and commands were introduced for this.

In year model 1995-fault diagnosis works in a similar way to previously but with different diagnostic trouble codes and wider options.

Some important points to remember:
During fault diagnosis in the microprocessor system, memory sectors can become distorted and give unusual symptoms. In order to erase all unusual symptoms, the ignition should be switched off for at least 35 seconds.

Read and note all stored diagnostic trouble codes before disconnecting the battery or Automatic Climate Control (ACC) control module.

Before fault diagnosis

Check the following before carrying out fault diagnosis:
- that the compressor drive belt is intact and correctly tensioned
- that air comes into the cabin through the air ducts
- that the flow of air through the condenser is not obstructed.
- that the compressor clutch engages and disengages when the A/C unit is switched on (outside temperature should be above +5° C). If the compressor is not engaged, the system can be emptied of refrigerant (pressure switch on desicant container prevents engaging) or there may be an electrical fault.
- applies only to year model 1985:
that the electric radiator fan starts when the A/C unit is switched on.