Pete Lech

I suspected that my oil cooler fan was not coming on, and confirmed it today. Even though the temp gauge went to 9 o'clock (250 degrees?) while idling in a Parade, the fan did not come on. When I got home, I pulled the headlight (thanks to this Forum for the great DIY pix) and disconnected the plug - the fan came on at high speed, so I know that the motor is good.

My question is: At what temperature should the fan come on? Even if the low speed resistor has failed, shouldn't the fan have come on on high speed when the temp hit 250? Could this mean that the temp sensor has failed instead of the resistor?

Interesting side note - when driving at moderate speeds, it is amazing how quickly the temp comes down even without the fan assisting.

964Cab

More than likely it's the CCU Climate Control unit as the slow fan speed is a function of the so called, "ballast resistor" and the hi speed operation is a function of the CCU. A Hammer ck up should reveal the status of your CCU relative to the hi speed oil cooler operation. ANDIAl is perfect for this problem.

Patrick

Randall G.

Hi Pete,

Kevin at Andial showed me in the '89 964 manual where it says the oil cooler fan is supposed to come on in fast-speed at 115C = 239F. That said, the 9:00 position is not nearly 250F--you need to get above the 10:00 position to hit 250F:



You can see that the oil has to get pretty warm before the high-speed fan will kick in. In a nutshell, I don't think just idling in the garage will get the oil hot enough for the fast-speed fan to start.

Oh, almost forgot to add that the slow-speed fan is supposed to start at 100C = 212F.

I believe your next step is to verify your resistor is intact. The resistor is in series (between) the oil cooler fan relay slow-speed power output and the fan. Thus, your fan will never run in slow-speed if the resistor is bad. Fast-speed operation simply shorts around the resistor (powered from a separate relay terminal). It's the voltage drop across the resistor that causes the fan to run slower (slow-speed). You can find instructions on how to verify the resistor is okay here:

<a href="http://members.rennlist.com/rgranaas/rgranaas.htm" target="_blank">Oil Cooler Fan Ops Summary</a>

Finally, Patrick is right about Andial being able tell if your CCU is the problem. They can use their "laptop hammer" (what's the correct name?) to try and start your fan, and read any error that pops up. As a matter of fact, after exhaustive troubleshooting of my own oil cooler fan, it was Andial that was able to confirm my suspicion that the CCU was faulty. Anyway, you can check the resistor yourself at home, as well as the relay and temperature sensor.

Good luck!

993C4

Hi Randall,

I've noticed that my slow speed fan does not kick in until temp guage reads around 220F -230F (around 9:30).

I had my car inspected recently by the authorize mechanic and my resistor and thermostat is working, but is it normal for the slow speed fan kick in at such hi temps?
Is there any way I can get the fan to start at lower temps?

Regards
993C4

Randall G.

Hi 993C4,

I don't think it's unusual for the low-speed fan to start on the high-side of 212F. For example, when Andial had the substitute CCU in my car, the oil cooler fan didn't start until the oil temperature was noticeably higher than the 9:00 position. It is important that the fan continues to run and cools the engine once it starts. Both E.J. and Larry N. have oil cooler fans that start, run for 10s or so, then stop. I believe they have resistors that are faulty, with only intermittent continuity.

Interesting question about trying to start the fan sooner. The oil cooler fan gets its power through a relay, and the relay gets it signal to reposition (power up the fan) from the CCU. The CCU knows when to start the fan based on the resistance reading it receives from the oil cooler temperature sensor. As temperature increases, the sensor's resistance decreases.

Soo ... to get the CCU to start the oil cooler fan at a lower temperature, you need to find a sensor who's resistance drops faster with temperature ... or has the same sensitivity, but a lower resistance at room temperature. I personally am not aware of such a sensor.

That mouthful said, there are a couple ways to run your fan continuously:

-Jumper the oil cooler temperature connector with about a 1k ohm or so resistor. Haven't done this myself, but can't see why it wouldn't work. Doing this will trick the CCU into thinking the oil is always 212F, and the fan will run continuously in slow-speed (unless the ignition is off).

-Disconnect the oil cooler temperature sensor. The CCU reads an open circuit, and runs the fan in fast-speed continuously (default setting).

-Install a jumper on the relay like I have done:

<a href="http://members.rennlist.com/rgranaas/Oil%20Cooler%20Fan%20Jumper%20Diagram.jpg" target="_blank">Slow-speed Jumper</a>

Now, in my case, since the CCU wasn't starting my oil cooler fan at all, it was either buy a new CCU, disconnect the oil cooler temp. sensor, or figure out a way to run the fan continuously in slow-speed. Thus, the jumper I designed. My experience has been is that it's nearly as effective (at least for non-track driving) as having the fan run continuously in fast-speed, but without as much wear and noise.

Finally, another option is installing a switch to run the fan at your leisure. Andial recently designed such a switch for Martin S.

Hope this all makes sense!

My Q Ship

The switch Andial designed can be used for either low fan speed or high fan speed. As Randall stated it can be used at your leisure and you don't have to worry if you forget to turn it off, the switch is ign. key accuated.
Q

993C4

Randall,

Tks for the info and it was pretty clear until you attached the circuit diagram. I don't have an engineering background and I would probably not perform such a task myself.

The on/off switch sound like a MUCH better option. Who can I contact at Andial and how complicated is the installation procedure?
Can it be purchased online?

Regards
993C4

Randall G.

Hi 993C4,

Here's Andial's website. You'll want to ask for (or address your e-mail to) Pete in service:

http://www.andial.com/

As for installation, I do know you need to knock/cut out one of the empty switch plugs in your dash to mount the switch. Not sure if the electrical portion requires splicing or if it connects to a terminal. The switch is pretty much hot-off-the-press, and when I talked to Pete last, he was still trying to find the time to put together the instructions for the kit. Also don't know the price ...

Perhaps Pete or Kevin @ Andial will jump into this discussion soon? (Though I do think MY Q Ship is Kevin?)

Pete Lech

Hey guys, lots of really great information here. Thanks to you all.

LarryN

Thanks to Randall for helping me troubleshoot that my resistors were both bad, my car is at Andial having them replaced today (along with other stuff). Anyway, seems that the resistor failure is quite common, possibly more so in the '95 year; I spoke to fellow 95' owner at a PCA breakfast the other day that had both his parts replaced within the past year.

Randall has all the info on this site but I just wanted to point out that checking for bad resistors actually turned out to be quite easy and only requires a multi-meter to measure the resistance between two relay terminals (with the relay removed). As Randall states on his site:

I think anything near .5 ohms would be indication that the resister is ok, I believe my bad ones measured about 20k ohms which translates to 'broken' given their intended purpose in the circuit.

So testing for bad resistors is easy but from what I've been told changing the out is not and the oil cooler side is the more difficult (although I know it's been done as a DIY).

By the way Pete, I've seen your car in the xmas parade pictures today and am now confirmed to be suffering from wide-body envy; very nice car.

Cheers,
Larry

Ken Wise

Larry,
I believe I have the same problem on my 96. What did they estimate the fix to cost?. Thanks.
Ken

LarryN

Ken,

Picked up the car last night, Labor was $280, Parts were $88.98.

Have attempted to add a picture of the bad ones (I was curious as to what they looked like myself).

fan resistor picture


I understand that the newer ones have metal backing on them to better transfer the heat to whatever they are bolted to - so they won't burn out so easily.

It's also speculated that the failures are more common in an area that has us stuck in traffic in warm weather and so on, where the fan is running almost constantly. I think the part is just plain weak as originally designed. Porsche should have probably had a campaign to replace them all (IMO).

Hope this helps,
Larry

E. J. - 993 Alumni

Thanx Larry, Did you watch them do the work? I am curious if they had to remove the bumper cover to get to them. I don't think you have to. Also, let us know about your oil temp in traffic from here on out.

Randall, Is it safe to assume that if this is the fix for Larry, then I should do it too? I don't remember what our diagnosis was on my car.

Thanx,

E. J.

LarryN

Did not watch so I'm not sure if the bumper cover was removed. Will keep you posted on what I notice in terms of oil temp differences.
-Larry

neunelf

Larry,
Do you by chance know if 'the newer ones' were introduced during a production year or are a post 993 production improvment?
Thanks