Cayenne S (9PA) V8-4.5L (2003)
Control Module HVAC: All Technical Service Bulletins
A/C - Erratic/Inoperative Auxiliary Heater Operation
Cayenne
2/03
8220
Binder - 8, Air Conditioning
Date: 12-18-03
Diagnosis And Repair Of The Auxiliary Heater
Vehicle Type:
Cayenne S/Cayenne Turbo
Model Year:
As of '03 (3)
Concerns:
Diagnosis and repair of the auxiliary water heater (auxiliary heater) (I No. 7VE, 7VL).
Information:
Below are instructions for troubleshooting complaints in relation to the auxiliary water heater system. Software version 16.0 or higher is required for
the work with the Porsche System Tester 2 (PST2).
Note:
Low voltage cutoff (--> step 2, remedy for cause 1) can be changed in the auxiliary water heater control unit using the PST2 only with software
version 17.0 or higher.
Work Procedure:
1.
No reaction to the "Timer" button.
Cause 1:
Software error in air conditioning control module.
Cause 2:
Air-conditioning control module faulty.
Remedy:
Replace air conditioning control module.
2.
The auxiliary water heater cannot be started.
Cause 1:
The auxiliary water heater does not start because the battery positive voltage is 12.2 V
or lower (--> Undervoltage cutoff of the auxiliary water heater). Fault memory entry
"1444 - Undervoltage cutoff" in the auxiliary water heater control unit.
Remedy:
Charge the battery or replace it if faulty. Change the undervoltage cutoff from "External"
to "Internal" in the auxiliary water heater control unit using the PST2 (--> PST2 software
version 17.0 or higher required).
Cause 2:
The auxiliary water heater was disabled or switched off by a protective function. This protective function is stored as an entry in the
auxiliary water heater control unit (e.g. "1406 - No firing" or "2251 - Control unit disabled").
Remedy:
Read out the fault memory with the PST2. Remedy the fault or faults as described in the Cayenne Technical Manual, Group 8,