Mr.Alex

Recently fellow Rennlister Cobalt let me stop by his house to help me out by using the Hammer tool to diagnose a bad O2 sensor. But at the same time the computer said my oil cooler fan was 'seized', which is not good obviously. Since there aren't too many variable I thought this could be kind of an easy fix.

Here are the facts:
- Removed heat from the car so I pulled the 'rear' blower relay over the winter break.

- Changed the ceramic resistor with the updated one last summer when swapping oil cooler.

-Swapped the oil cooler relay with the AC relay. Started ignition and AC fan runs with both relays.

-The 25A fuse for oil blower is good. (Although some sites say it should be 30A, can confirm?)

-Used jump wire to test the resistor, runs at both low and high speed.
-Disconnected the wire to the resistor and jump wire would not run in low speed.
-Connected my old resistor and same results; fan runs both low and high speed with jump wire.

-Disconnected temp. sensor on oil cooler and turned on ignition. Fan started running in high speed after a minute. So I assume the temp sensor is good.

-Fun fact; AC fan will not run if oil cooler relay not plugged in.



Anybody go through the same thing?. I've already been texting cobalt so often his wife is probably suspicious.

Could there be some wacky link between me removing the rear blower relay and this? I assume the fuse, relay, ballast resistor, and temp sensor are all the variables, unless the CCU can be causing this?

Spyerx

subscribed. i'm not 100% certain mine is working, as i've never seen / heard / felt it turn on. hottest it has gotten is about 1-2 needle widths below the 2/3 mark line on the temp gauge however.

Navaros911

Spyerx,

If you have access to a diag computer you can run it on both speeds. Or use the jump wire test... I think described here on some threads or you can go by Adrian's book. Both are very easy tests.

Navaros911

Since the fan runs, it can't be seized... So I think you should question where the fault code comes from.

The CCU is the brain and probably sends the fault code... So perhaps that's where the problem lies.


I did't quite understand if the car has cooling issues. It seems like it has a fault code, bit nothing else is a problem.

So is a CCU that sends a wrong single fault code, but the car functions as intended really a problem?

Sometimes we get obsessed with fixing things on these objects of passion that we forget the best therapy for that obsession is to take it for a drive - I just came back from one 😎

Mr.Alex

Easiest way is to just use a jump wire, or just let it sit so it heats up and see if it runs. You'll know when it runs, its loud and if you place your hand under the bumper you'll feel the strong air flow.

http://p-car.com/diy/fan/

At the moment I don't have cooling issues, but the weather has been kind of cool and I have not gotten stuck in traffic yet. The problem is that I can induce it to run with the jump wire, but it won't turn on by itself when its supposed too.

After everything I tried today I had thoughts about the CCU, although the thought of CCU issues made me cringe. Is there a troubleshooting page for CCU anywhere, or is it pretty much just bite the bullet and replace?



PS: I read somewhere that turning on the AC turns on both the AC fan as well as the oil cooler fan. For the sake of diagnostics, can someone with a working oil cooler fan try this? Can just use the ignition and not turn the car on.



edit: found Tore's page on CCU's

ToreB

No need to replace CCU.
First of all, the oil temperature sensor is placed on the oil line by the radiator/cooler, but the oil needs to circulate here for the CCU to start the fan. The oil thermostat in the engine must open at the correct temperature in order to start circulating the oil to the radiator. If you see issues in engine temperature, a failing thermostat might well be the culprit.

If the CCU is generating a fault code for the oil cooler fan, you either have a non-op fan or circuit, or the feedback circuit to the CCU might be damaged. This can be checked with an ohmmeter at the CCU harness connector. Pin G9, green/blue wire shall be connected to the blower motor.

The CCU oil temperature sensor can also be checked with an ohmmeter. Measure between G12 and G18 sensor GND, you should read about 22.6kOhm at 20deg C, and about 4k at 60Deg C oil temperature.
Early 964 CCU's do not have a OBD-invoked test feature that allows running the fan.

Cheers,
Tore

Mr.Alex

Thanks Tore for always coming to the rescue on these things. So my multimeter came in yesterday and I pulled out the CCU today after a small drive. With the ignition on the temp gauge was at about the first mark (pretty cool) and crossing pin G12 and G18 gave me around 14.6k Ohm, so I assume the temp sensor is pretty alright.

But what do I cross the G9 pin with? I tried G18 just for kicks but nothing happened. Do I need the car to be running and up to temp for this?

On side note; do you believe I have to keep the little CCU fan if I removed heat from the car? Considering temp **** always on max cold.

Spyerx

i have same symptoms, every diag the cause?