rod635

Hi, yes checked it with fan on low and high and at high & low temp. Fans in the front are blowing but not the rear. is the CCU unit at fault?

ToreB

You state you have no power feed, I guess this means that there is no permanent +12V on fan relay terminal 30 and 30c. Terminal designators is printed on the relay.
This power feed is a thick red wire coming from the starter/generator. I haven't digged deep in this particular part of the car so I don't know where the junction is. I guess it should not pose big problems to trace it. Maybe others can chime in if they know where these wires are routed, maybe it is a simple eye connector on the generator. I have seen previous cases of severe corrosion/damage on the generator wires.
Cheers,
Tore

rod635

Thanks for your replies. I'm a newbie to these cars, I'll check where the generator contact are and check these. If anyone else has any suggestions please let me know.

rod635

OK feel a bit like an idiot. Decided to test relay & fuse again and it turns out I had a faulty lead on the multimeter. So what I have is Power at the fuse, on relay at terminals 86, 30c, 30. If I take the cap off the relay and manually close the switches one of them activates the fan. I tested the relay off the car and it seems fine. Should terminal 85 be an earth as if I test this with one of the live contacts I get 0 current. Also if I join the wires on the resistor or earth them nothing happens, is the resistor an earth circuit? If I join or ground the resistor wires should it ground contact 86?

The car does not have AC but it has a AC CCU

ToreB

Good. Did you do the rear fan test as described in my DIY page linked above?
Remember, when testing at cold engine, the fan will only run if you set the temp to max.
T

rod635

Hi, yes followed those tests today, this is what I found today,

Ignition or off off
jump 87 & 30 and fan runs
30c 87c fan runs when resistor wires touched together

This happens when Temperature is turned to hot or cold

Should 85 & 85c be getting power from the CCU?

ToreB

If the fan does not run when activating the low speed relay, unless the resistor is shorted, the resistor needs to be changed. It is not very expensive, and I never bother to reset or try to repair the thermofuse on the resistor.
However, it seems that there are more problems than just the resistor.
Terminal 86 is the +12V side of the relay coils, and 85 and 85C shall be grounded when the CCU activates the fan on full and low speed.
Does the CCU otherwise work normally, main blowers work, servo motors move? If so, the CCU relay outputs might be damaged, this is indeed repairable. However, I very seldom see that both have failed.
You could try to measure for the GND signals at the CCU harness connectors, pins K19 and K25. Which part number is your CCU? If it is a 993 unit wiring changes are needed to get it to work in a 964, but this should not affect the operation of the rear fan, at least full speed operation. Depending on CCU 993 part number, up to six wiring changes are needed to get the unit to work properly. The one who installed your CCU might have screwed this up, damaging the rear fan relay outputs.
Cheers,
Tore

rod635

Thanks Tore, I have only recently bought the car, there are a number of electrical items not working to challenge me. Also on the list are mirrors and headlamp washers.

Regarding the blower I pulled out the CCU, pin K19 had no power K25 had power, please see photos of the unit attached, would you know if this is a 993 or 964 unit?

ToreB

It seems that the part number label is gone. This is a 993 unit indeed, easily determined by the double A/C switch. There are two main versions of the 993 CCU's, (part number ending with 00 and 01) and they are not easily determined by inspecting the circuit boards inside. The easiest way is to use a Porsche compatible OBD tool to read out the part number.
I am not sure what you mean by power on the fan relay outputs, these are open collector outputs, and you should read +12V on the output when not activated, and 0V when the fan is supposed to be on. The fan relay must be installed when doing this test, and of course the ignition needs to be on.
Cheers,
Tore

rod635

Hi Tore,

Firstly thank you for all your help.

On the CCU connections K&G is there a way to bridge the connections and operate the fan to make sure the wiring is OK

I wonder at this stage should I buy a 964 non ac control unit and sell my 993 one.

ToreB

It is indeed possible to get your CCU to work in your car. Non-A/C 964 units are seldom seen, at least here in the Nordics. (which should be the opposite really!)
You could just unplug your CCU and ground pin K19 and K25 at a time to get the rear fan to run in two speeds.
Cheers,

rod635

OK, just so I don't set my car on fire, if I get a piece of wire and ground it and touch it off pin K19 or K25 the fan should turn on.

ToreB

Yes, just connect a wire bridge between K1 (GND) and one of the two pins.
Here's a pic of the connectors:
T

rod635

Hi Tore,

I hope you are keeping well.

You recently advised me on a issue I had with my 964 rear blower not working. Turned out I had a 993 ACC in a non ac 964, I replaced it with a 964 non ac acc and the blower now works, yay.

Problem now is the battery has a drain on it that disappears if we remove the HVAC fuse

Any ideas whats causing this?

Regards

Rod

ToreB

Hi Rod, all is well, thanks.
The Climate Control Unit is supposed to stay on for up to 20 minutes after ignition off.
If it does not shut down, it is due to an internal component failure. This can indeed be fixed. I'll send you a PM.
Cheers,
T