Radiator Fans - again
 

Just got my car back after getting my radiator fans checked - and my mechanic still insist that my fans are fine....

The problem (if it is indeed a problem) - sometimes only one of my 2 front radiator is on... at low speed. If the fans are spinning at high speed it's both on.

My mechanic says if the aircon is on, both fans are on. If aircon off or compressor off, and the engine is hot, one fan comes on. If engine really hot, both fan comes on at high speed.

Is this true ? I still can't figure out if this true...I seem to randomly have only one fan on... The temp has never crossed slightly more than 90 degree C, so technically it hasn't overheated. I'm just worried the series resistor is on it's way out.

(I know I had posted in someone else's thread on this, but wasn't clear on the answer. Wanted to be sure in case I overheat the box one day)

each fan has its own thermostat; they operate independently from one another unless the AC is on.

Just interesting learning. Seriously, what kind of engineering is this mate?! Another added possible point-of-failure or just cooling based on the Left & Right wind direction? fak sake....

shlim8's mechanic should have designed the cooling system, it would have been simpler and perhaps better imo

Thanks insite for the reply.

Any ideas on what the part no is for the thermostat and where the thermostat is ? I re-looked at the pet catalog diagram and can't find a thermostat anywhere around the radiator. The thermostat should be measuring the temp of the coolant in the radiator (like normal cars) ??

If I have a radiator fan that seems to be on more often than the other side, does it mean that radiator is less efficient in cooling or hence fan is on, or the thermostat on the other side is not working well ??? Or water flow is less on one water pipe.... hmmm

In fact I've never had the left side fan come on without the right side fan being on (but the reverse happens).

Nothing is simple on a P car isn't it ??

I think it actually measures the surface temp of the the radiator itself. The part number is 996.616.101.00. I actually have my radiators out right now; I'll take a pic tomorrow.

The fans in my 2000 S seem to work together. I've never noticed only one fan operating. The Durametric can bring them on in high or low but not independently. I could see if the big resistor failed on one fan you'd get a situation where both fans would run in high, when the resistor isn't used, and only one fan would run in low.

I'm not saying you're wrong, only giving my experience.

That's actually the series resistor... I'm going to order those online and replace it just to be sure...

They do call it a resistor, but it looks like a thermistor to me. I bet yours has failed.

My fans have finally gone crazy....

Yesterday when I started the car from cold, the fan comes on - as the a/c was on, I thought it was normal... checked the front and only 1 fan (right side) was running at low. I turned off the a/c and the fan now goes in to high speed AND again it was only on the right side...

Drive for the next hour or so, stopping where ever possible to check the front fans - still only 1 fan running at either low or high... (so at this point in time I'm thinking great, it's much easier to fix a permanent problem that an intermittent one)

When I got home, both fans are on at high speed... I let it run till it cuts out. Then I turned the aircon on, both came on at low speed.... $#@!!

Summary:
Engine cold - a/c on = one fan on low, sometimes 2, a/c off = one fan on high, sometimes none
Engine hot - a/c on = sometimes one fan, sometimes two fan
Engine very hot - sometimes one fan on high, sometimes two fans on high...

Any ideas ? I'm still thinking that something must trigger the fans, the dme ? But the dme must get it's temp input from somewhere. Or could the relays cause this ?

The series resistor might explain one of the fans not coming on at low speed, but now the other fan is intermittently coming on even on cold starts ?? (at least fans coming on excessively is better than not coming on at all !!!)

Where are the relays for the aux fans ? Are they in the back trunk ? And which one ?

I saw a bunch of relays in the left rear corner of the trunk when I had all the trim panels out the other day but I don't know which, if any, control the fans. There was a little diagram as I recall.

Looking at spec sheet 5 (circuit diagram) for you it looks as if you need to go to the dealer and get them to initiate a full Cooling & AC systems test on yur Box. This is done from their PIWIS Tester II only.

There are relays for everything:

Cooling water Blower Motor 1 relay
- Relay Step 1
- Relay Step 2

Cooling water Blower Motor 2 relay
- Relay Step 1
- Relay Step 2

Ther is also a 3-lever cooling water switch which gauge low/high pressure and mean pressure. Those are linked to the relay circuitry.

Your problem could be anything in that range. To pin point it to the source, only the PIWIS tester II will be able to detect your fault.

Other than that, you have to rule out one-by-one and perhaps end up changing all the relays before getting to a point where it's not fun anymore to DIY. I've been there done that a few times :/

at least to answer your question:

http://www.revrush.com/986/relaybays.jpg

Hope this helps a bit mate and luck on the fan thing. Getting hot in S'pore :/

I just replaced the fan resistor and it cured the problem of only one fan working on low speed.

Thanks san rensho and madmods.

My resistor has arrived but me and the car is still out of town till end of next week. It's scary to play roulette with my fans ( sometimes on / off). Good thing is that the temp is only slightly higher.

I have a good feeling you are a very lucky guy! The proof = you have a Porsche car ;)

Regardless of a fully functioning cooling system or not, I believe this car was designed for the north (very north) European countries only. When I turn on the A/C the water temp goes straight up it feels as if the engine will blow-up to the moon. I wouldn't be surprised the coolant/water is hotter than the engine itself :/ Go figure..... still a nice car tho!

Best of luck mate and take care there

yes it true that when engine is eally hot both fans on at high speed.

Yes, that's consistent to my car too. But now I've finally had a situation where only one fan is on at low speed with the a/c compressor on. And I've got one fan coming on at high when I start up from cold in the morning. So I'm sure I've got a problem (or two). Going to change the series resistor this friday.

Hopefully this will give me more consistent water temp... and colder a/c

Got the resistor replaced. Been running around for a day now. Looks like both fans are on now, as san rensho noted - it looks like the resistor was the problem.

Its probably a combination of cleaning the radiators (10 yrs work of junk!) and both fans coming on - the temp is now quite consistent at slightly pass 80C. But no chance to push the car yet as I'm still bedding in the front brakes after converting to the S front brakes.

Great news!
Can you post up the P/N for the resistor ?