Sysgen

Here's a weird one, I've had the car for 4 years, never had any issues with my fans. One day coming home after work I turn off the car and the fans continue running like it does when hot except this time they alternate between slow speed and fast speed about every 5 seconds non stop. Very annoying.

I had a spare relay so I put it in but this one keeps running sometimes and drains the battery.

I got a third one and same symptoms as the first one !! Slow, fast, slow, fast.

So first relay is 944.615.104.03
Second is 944.615.104.01 <-this one is much smaller and older
Third 944.615.104.03

Anyone ever seen those symptoms? Could I have two relays with the same symptoms or could there be a problem somewhere else?

TIA

bigcigarjeff

when was the last time you replaced the radiator fan switch ?

Sysgen

The fan switch? You mean the thermocoupe in the radiator? 2 years ago.

smokin_944

My understanding is that if the thermal switch goes bad, the fans don't go on, or they don't shut off til the battery craps out.

wolff

Yeah, my thermo-fan switch failed in the "on" position (5 sec cycles) a couple of years ago. Got coolant all over myself while replacing (doh!). Problem solved, however.

968gene

fan relay ($$$$)
There is a fairly straight forward troubleshooting paper out there on the web...PM me and I'll email it to you.

sweetskillsrk

If it was me I would start troubleshooting with the least expensive parts. Sometimes I end up troubleshooting by replacing the part. That doesn't always work so I have sometimes extra parts but never anything that was too expensive or I can't use. If it was me I'd start with the $15-$20 fan switch and try that first, as I'm sure you know those are notorious for going bad. Even though you replaced it 2 years ago you never know. Just a thought. Good luck.

Sysgen

So they were cycling slow and fast every 5 seconds? That's exactly my problem! I'll replace the switch and see. It's just weird that depending on what relay I use the symptoms change.


Done that and they all pass the test.

Will do. I think there is also a way to test it using hot water.

Thanks everyone.

968gene

"Done that and they all pass the test."

If you followed the paper I am referring to, then you have isolated the issue.

Toran

Is your radiator fan resistor in good condition?

wolff

Correct. At the time I thought that it was 5-on-5-off repeated, but that's also what I thought the normal cool-down behavior was, for lack of a better description. (More research shows that what I thought sounded like "off" is actually a slow speed, which make a lot more sense anyway.) In any case, it seems like the same condition and thankfully the part is pretty cheap. Good luck.

Sysgen

Hum, never checked actually. What would be the symptom? Don't they run always fast or always slow if the resistors are dead?

Cool ! That's the beauty of Rennlist right there ! I was hoping to find someone with the same issue and there you go ! I'll order it this week.

Toran

radiator fan resistor

"What this corrosion does is allow the car to run hotter because there is no low speed. Also because of the corrosion, the wiring itself gets hot and burns off the insulation that covers the wiring"

From:
Late 944 Low/High Speed Fans Operation Not Working

Bill Lucas

The wires get corroded up near the battery compartment. Clean those wires. It's what caused my fan cycling problems a couple of years ago.

Sysgen

Ok, easy enough to check, I'll go right now actually.