PORSCHE 964 HEATER CONTROL UNIT PROBLEM
08-28-2010, 06:32 PM
#1
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PORSCHE 964 HEATER CONTROL UNIT PROBLEM
HI I HAVE A 964 C4 CAB AND THE HEATER CONTROL UNIT HAS A SMALL FAN ON THE BACK OF UNIT WHAT DOES IT DO? IS IT TO COOL THE UNIT OR DOES IT HAVE ANOTHER FEATURE OR PURPOSE?
BECAUSE THE FAN STAYS ON EVEN IF THE IGNITION IS OFF AND DRAINS BATTERY BUT IF I DISCONECT THE TWO PIN PLUG ON BACK OF UNIT THE FAN STOPS.
PLEASE HELP!
BECAUSE THE FAN STAYS ON EVEN IF THE IGNITION IS OFF AND DRAINS BATTERY BUT IF I DISCONECT THE TWO PIN PLUG ON BACK OF UNIT THE FAN STOPS.
PLEASE HELP!
08-28-2010, 07:29 PM
#2
Three Wheelin'
The fan on the rear of the CCU is part of the temperature sampling system. It draws air through the grille on the front of the unit so that it passes over a thermistor sensing the cabin temperature. The fan is supposed to run for something like 15-20 minutes after ignition switch off but can be caused to run permanently through the failure of a driver transistor in the CCU.
If you disconnect the fan the effect is to disable (or, at least, minimise the effect of) the temperature sensor and the cabin temperature stability will suffer - usually getting colder over time.
Regards
Dave
If you disconnect the fan the effect is to disable (or, at least, minimise the effect of) the temperature sensor and the cabin temperature stability will suffer - usually getting colder over time.
Regards
Dave
