Westyman

Hi guys,

Bringing up an old topic here about the fabled oil cooler fan resistor but it has got me thinking after I was stuck in traffic and noticed my oil temp rise.

I've got some conflicting information on the oil cooler fan and am getting confused.

I've searched this forum and found lots of useful info on the cooler fan and also read the http://p-car.com/diy/diy site.

1. If I look at the pictures of the oil temp guage on the pcar site then my fan is kicking in at the same place and corresponding with the temp the fan is switched on, which leads me to believe that the fan is operating as it should.

2. If I do the relay jumper test then I can only activate the fan when jumpering the terminals 30 & 87 (bottom solenoid in relay the fan is activated).
Crossing terminals 30c and 87c doesn't do anything nor does crossing terminals 30 and 87c as suggested by p-car (however looking at the relay jumpering 30 & 87c will not work as one pole is for the top solenoid and one is for the bottom), which leads me to believe that the fan is not working on slow speed stage.

3. Some of the postings state that the cooling fan should activate at the 8:30-9:00 O'clock position. Otherwise,the fan will activate at higher 10:00-10:30 temperatures. Are we referring to 964's here or 993's?

The 964 switches it's low speed fan on at 212F and high speed at 239F whereas the 993 switches low speed on at 230F which would indicate above 9 O'clock but before 10 o'clock on the guage. Also there is no known temp listed in the manual for the 2nd fan speed.

4. A friend of mine who is a P mechanic at a main dealer says the fan only operates at one speed and this is also confirmed by a colleague of his at the garage. The manual I have states that it is a 2 stage fan but only gives the fan switch on temp at 230F and no other data to say when second stage would kick in.
Also my manual doesn't show a resistor for the oil cooler but my PET catalogue does.

So could it be that the oil cooler in a 993 is a 2 stage fan but only operates at one speed?

Sorry for the long post.

Thanks

John

Crimson Nape Racing

It is a 2-speed fan. Mine only worked on high speed when I got the car (following the P-car instructions). After replacing the fan ballast, both low and high speed worked for about a year. When the ballast went out the second time, I did the high speed fan switch mod in lieu of replacing the ballast again.

Westyman

Thanks for the reply Bob,

Where was the needle on your oil guage when the fan kicked in prior to changing the ballast resistor?

When you replaced the ballast resistor was there a noticeable difference in the two fan speeds?

Thanks

John

fbfisher

I think the two speed fan is a silly design flaw. The cooler the better AFAIK, therefore, high speed when cooling is needed is what is necessary if you live in all but the coldest climates. Why wait for your car to get up to 10-10:30 before the fan kicks in? I always found this disturbing. Read my recent fan switch post, do the mod and enjoy your car running at warm and cuddley 8:00.

Crimson Nape Racing

John - before changing the ballast, it never got hot enough for the fan to kick in. Fbfisher is right, do the fan mod!

Randall G.

There's no doubt it's a 2-speed fan. The ballast resistor is in series with the fan when going through terminal #7 on the relay plug, creating a voltage drop that slows the fan speed. Fast speed operation (through #5 on the relay plug), does nothing more than shunt the resistor, placing a full 12V at the fan, instead of a reduced voltage.

If you look in your shop manual's electrical diagrams, you will find the ballast resistor, Sheet 3.

My best guess is Porsche added the slow-speed mode because it's much quieter (not that any of us care). Technically, other than a smaller electrical load, I can see no advantage to having a slow-speed mode. Even with respect to the A/C condenser blower. Is it possible to have too much cooling of the condenser? I don't think so.

Hope this helps...

Edward

I WAS thinking of replacing the resistors, but as was said here and in a previous thread some time ago, if the high speed kicks in past 9 or 9:30, I see little point in going through all the trouble when a manual switch can put the issue to bed (for me, anyway )

Edward