a993lad

Hi guys,

I'm still trying to sort my oil cooler so grateful for any tips.

The story so far:

Oil cooler fan is running at high speed whenever the ignition is on, even if the engine temp is stone cold.

I have so far checked:

Relay - seems fine as I've swapped it out for two others that I know are okay plus a brand new one.

Fan - seems to function correctly as I have tested it by removing the relay and bridging the connections to achieve slow speed and high speed function.

Temp sender - I've disconnected the existing one and plugged the wire connector into a brand new sensor (not fitted into the rad) but the fan still runs high speed.

Why is this fan running all the time?

As it's winter here, would it be better to remove the relay so the fan is always off rather than have it always on high speed?

Thanks

Marc

tommyg

Oil cooler resistor is bad.

ToreB

Tommyg, he has already tested the slow fan function OK, thus is his resistor OK.

The CCU is controlling the oil cooler relay, you might have a problem there. Simplest way to find out: Remove and disconnect the CCU, the fan should stop. If it's not stopping you have a cabling/short circuit somewhere in your car.
You could measure the Oil cooler relay outputs, pins K10 and K22, wire colours green/red and brown/red. See if K22 is always +12V. If so, you could have an internal problem in the CCU. It's certainly possible to fix, have a look at my CCU DIY page:
www.ccu.tore.bergvill.com
Cheers,
Tore

tommyg

Good point Tore - missed that.

Cactus

I heard when these resistors go bad the fans automatically run on high speed like you describe. Is this correct?

ToreB

Yes, the fan will run intermittently on high speed if the resistor is shot. It's quite simple really: The CCU will start running the fan on low speed when the oil is warm enough. If the fan fails to run due to a shot series resistor, the CCU will soon start high speed to increase the cooling effect since the temperature is not decreasing. Once the oil gets less warm, the CCU will revert to low speed again, which really is a stationary fan. And so on...
The CCU should not start the fan when the oil is cool.
By the way, the fan control outputs in the CCU is IC13, a CA3262 high current driver. It's fairly easy to change, but more important, a lot cheaper than changing the CCU!
Cheers,
Tore

a993lad

Is the ccu the climate control unit in the dash?

If so, why does that control the air cooler fan for the engine oil?

Also, am I better off running without the fan at the moment rather than having it on high speed all the time?

Marc

axl911

I also think the problem is the wiring to the CCU which controls the fan.

There is a wire from the oil cooler temperature sensor to the CCU. When this wire reads high resistance, the oil temperate is hot. The CCU will turn on the fan depending on the oil temperature or resistance reading from the sensor.

If there is a break in the wire, the resistance will read infinity or open circuit. This will make the CCU thinks the oil temperature is extremely hot and make the fan runs high.

I manually activate the oil cooler fan this way, by breaking the wire with a switch. This feature is well documented with various DIYs.

Locate that DIY and put a multimeter on that wire, I think you will find it reading very high or infinity. This would indicate a break in the sensor wire. And this makes your CCU think the oil temp is hot...and it turns on the fan.

axl911

Here is the diy procedure for the oil fan switch.

http://pcarworkshop.com/index.php/99...verride_Switch

You need to test the resistance at the green/black G12 wire in Step 3 of the DIY. Don't bother testing at the sensor yet since you don't know the condition of the wire to the CCU. If it reads infinity, then you have a wiring problem to the sensor and/or the sensor itself if bad.

If you get a valid resistance reading, then the CCU is may be bad. It shouldn't turn on the fan until it get a high enough resistance value.

Another place to look is the oil cooler relay. But you already look at that.

ToreB

I agree with axl911. Check the oil temp sensor resistance, use an ohmmeter and connect it to GND and the G12 wire. It should read about 22kOhm at 20degC and 4kOhm at 60 degC. (that's the oil temperature)
Disconnecting the oil cooler fan would be potentially dangerous, and at least would need close attention to the oil temp gauge.
The Climate Control Unit is in the dash, yes. This controls all fans in your car.
Cheers,
Tore

a993lad

Thanks guys

Looks like I am taking the ccu out this weekend then.

Marc

kjr914

a993lad,
No expert on this here, but when I run the car hard I pull the plug in the front right headlight area that turns the fan on all the time, just as you describe. Perhaps double check this connection, ensure its a clean electrical connection. If its disconnected or corroded, it might be "open".
http://pcarworkshop.com/index.php/993_-_Oil_Cooler_Fan

embacpa

i have an 89 3.2 that i wish the fan ran high all the time.

a993lad

Right - I've temporarily solved my problem with the oil cooler fan being on constant high speed - by simply removing the relay. The temp is never getting higher than about the 7 oclock level as its winter here.

But I recognise this solution is ueseless if summer returns or I get stuck in traffic!

So I must fix it. As the relay and the temp sensor are both fine I have no option but to start delving in the ccu and would be grateful for some more advice.

Pulled the ccu out of the dash today but could not easily remove the two wiring plugs. is there a nack to getting these out? There's not much spare cable to play with so it's not easy to see what holds these connector plugs in the unit.

Once I get them out, what wires do I need to check? The replies above refer to G12, K10 and k22. I confess I'm a bit confused.

Thanks for any help/advice.

Marc

ToreB

My DIY page linked in my first post in this thread explains the K and G connector placement.
The two connectors sit very tight: Press the release catch. There's a small opening between the catch and the connector. Stick a small screwdriver in there and help the connector out.
But, before you disconnect it, be sure to do the measurements mentioned above. Check sensor input and relay output.
Cheers,
Tore