Initial Inspection and Diagnostic Overview

General
The heater and/or air conditioner can be checked with a 9288 System Tester or 9268 Tester.

Information for 9268 Tester:
- The 9268 tester is connected in the 19-pin diagnosing socket with help of adapter leads 9268/2 and 9288/1.
- The fault memory of the DME control unit must be read first. The fault memory of the heater and/or air conditioner can be read only after 1500 (no faults stored) or 1000 (end of output) is displayed.
- If the control lamp for the airbag system indicates a fault, flashing code diagnosis with the 9268 Tester will not be possible. Diagnosing is then only possible with a 9288 System Tester.

Explanation of Four Digit Fault Codes:
- 1st digit: 8 = Heater and/or air conditioner
- 2nd digit: 1 = Fault existing at moment 2 = Fault not existing at moment
- 3rd and 4th digit = Fault code

Troubleshooting requires that the person testing:
- Knows the location of components, function and interrelation of the systems being tested (model information),
- Is capable of reading and evaluating Porsche wiring diagrams,
- Knows the function of circuits and relays,
- Knows how to operate and read testers such as oscilloscope, voltmeter, ohmmeter and ammeter.

Important
- If a faulty component appears in the display of a tester or in the Fault List, the fault does not have to be in the displayed component, but instead could also be in the concerned control unit or connecting leads (paths) between the component and control unit. No troubleshooting may be carried out in the form of disconnecting plugs and so on before reading the fault memory, since this could be stored as a fault in the fault memory.

Displayed Condition on Tester
- "Fault does not exist"-- this could mean: Fault does not exist at time of testing (loose contact)
^ Remedy: Path checked by visual inspection

- Conditions, with which the fault had occurred, are not given (e.g. ignition not turned on, AC button not pressed)
^ Remedy: Compliance with the conditions displayed in the tester

- "Signal unplausible"--The control unit cannot recognize whether there is a short, break or seizure of an electric motor

Conditions for starting the diagnostic operation:
1. Vehicle speed = 0 mph
2. RH mixing chamber temperature < 80° C
3. LH mixing chamber temperature < 80° C
4. Rear fan temperature < 95° C
5. Oil temperature < 105° C

Criteria for canceling the diagnostic operation:
1. Vehicle speed > 0 mph
2. RH mixing chamber temperature > 80° C
3. LH mixing chamber temperature > 80° C
4. Rear fan temperature > 95° C
5. Oil temperature > 105° C