Need some help

[racer959]

I have a 993 turbo. The dial on the dash that controls the blower fan for A/C and heat only works on low. Is there a blower resistor for this and where is it located?

[TMc993]

Porsche 964 / 993 CCU electrical repair

[flskala]

Tore's writeup above is awesome. The resistors & other issues are also covered in this thread also:

COMPLETE A/C Diagnosis - Rennlist Discussion Forums

IIRC, the resistor(s) are located in the front left wheel well.

[racer959]

This could also be experienced as too low air volume or weak fan operation.

This could be due to the rear fan is not operating as it should, and the CCU is shutting down or slowing the front fans as a safety measure. (don't ask me why)

Set temperature knob to minimum and operate the fan speed knob. The front fans should run normally. Set to fan speed 3 and slowly increase the temperature setting. The rear fan should kick in at high speed as soon as heated air is needed. (depending on ambient and cabin air temperature). If there's a fault with the rear fan, the front fans will either go down to low level or shut down completely. Check the rear fan fuse, relay, motor and low speed resistor. You can also use a Porsche compatible OBD tool to read out any fault codes.

Erratic front fan behaviour can also be caused by a worn CCU fan control potentiometer. Try fiddling with the control, and maybe press or pull the knob a little. See the CCU repair page for details.


Where is the rear fan that is talked about here? I'm a little confused.

[jg291446]

Sounds like a bad relay. Look in the fuse box located in the rear trunk, on the left side (left to the blower). When the relay is bad, you loose high speed fan in the cabin.

The resistor is located on the left, inserted in the blower duct (on the left side) on that same duct, you have the temp sensor, which is inserted on the top of the duct.

FYI, people who use rs duct bypass have to remove this relay. But in order continue to have a fully functionnal fan, they jump the terminals where this relay is located.

It could be the CCU but the probability is low. I would bet its the relay. And, by the way, you have 2 similar relays in your front trunk fuse box. So you can easily swap and see if you have high speed fan.

If you need pics, PM me and I will post it here.

Once solved, please post what was the issue.

[jg291446]

Here are some pictures with comments. I used pictures from Pelican parts, Rennlist and Tore's website.

Very easy to test if your relay is the cause of the problem. You have to swap the blower relay in the back with same relay that your car has in the front.



Picture of the rear fuse box. By the way, you need to unscrew 3 bolts that holds the cover of the box. But don't worry, they are attached to the cover so when you unscrew, they won't fall.



Here is the front fuse box :

[racer959]

Thank you so much. Good pictures. I sent you a pm.