AC off and on problem

[Dino44]

Hello all,
I have a 1994 911 Carrera 2 that I just purchased.
Maybe someone here can help me out:
The AC will turn on and blow cool air, but only sometimes. Other times it will turn on for awhile and then shut off, only to turn on again at a later time while driving.
I haven't found any pattern to the intermittent shut-offs, but it seems to not work very well when it is the hottest outside-perfect!
Any help or advice would be appreciated from those who frequent this forum.
Thanks,
Dino

[Don Plumley]

Sounds related to your relay problem. 964's do have notorious HVAC ghosts. Here's a nice article on the servos

[computamedic]

It's possible that you may have a problem with the ballast resistor for the condensor fan. A faulty resistor prevents the condensor fan running at slow speed so the condenser temperature quickly rises to the point where high speed is required. THAT will work (and be quite noisy) but will stop quite quickly since the larger airflow will reduce the condenser core temperature quite rapidly. This may explain your "intermittent" fan noise from the other thread too!!

The condenser ballast resistor it mounted on the top of the condenser and is right underneath the battery vent tube - ideal to catch corrosive gases!!

Regards

Dave

[bazar01]

Originally Posted by Dino44

Hello all,

The AC will turn on and blow cool air, but only sometimes.
Other times it will turn on for awhile and then shut off, only to turn on again at a later time while driving.
I haven't found any pattern to the intermittent shut-offs, but it seems to not work very well when it is the hottest outside-perfect!
Any help or advice would be appreciated from those who frequent this forum.
Thanks,
Dino

You need to give more details.
Does the inside blower stops when you said it turns on for a while then shuts off?
Or only the cooling is lost but the inside blower is still blowing air?
Does it happen when the car is at idle or cruising at speed?