Daniel5691

Hello experts:

I have surfed through the Rennlist "search" function here, and I have read section 19 of the WSM (twice)... but still need a friendly nudge in the right direction, please...

1981 928S euro manual trans, and in all the short trips I have driven thus far, through Fall and a rather mild Winter (so far!) I do not believe my electric radiator fan has ever turned on even once.

I have never heard it cut on during running, in motion or at a stop, and I particularly noticed a lack of electric fan sound this weekend as it sat idling in my driveway for 15-20 min while I goofed around trying to aim my headlights.

Also, I have never heard the fan running after turning the engine off.

My engine temperature gauge will hover just below the "top white hash mark" but has never exceeded this value, the needle has never entered the "red".

What should I do first to determine if my electric radiator fan is functioning correctly?

Thanks in advance.

Dan

hwyengr

Just to clarify a point, your car has had its factory belt driven puller fan replaced with an aftermarket electric fan? Or, are you talking about the A/C condenser fan?

Daniel5691

Jeremy...
please forgive my poor description.
The forward-most fan which is not seeming to ever engage.
The belt driven fan which sits between the radiator and the engine is stock.
I mistakenly called the ac condensor fan an "electric radiator fan", and yes it is the one that never turns on.
I noticed in my son's 944 that his electric fan cuts on frequently, especially when the car is sitting still... and mine never does....
Thanks!

bureau13

If it's like my '86.5, there is a fuse, a relay and a temp sensor, any one of which could prevent the fan from coming on. As I understand it, it should run whenever the AC is on or whenever radiator temps reach a certain point. Check the fuse, then find the temp sensor (lower driver's side on the front of the radiator and jumper that with the car running...if the fan comes on you likely have a bad temp sensor.

Again, this assumes it's like mine...I have the same problem but haven't really got around to diagnosing it yet, as it's not hot here right now and I have no working AC anyway...but I did accidentally find a missing fuse and a missing relay, as well as a finicky temp sensor connector, any one of which could have prevented it from working.

hwyengr

The belt fan does almost all of the radiator cooling, so you'll rarely see the electric fan turn on unless it's really, really hot outside. If the belt fan keeps the coolant below the upper white line, it'll never turn on. Usually the only time I've heard the electric fan come on is for after cooling after you've shut down the engine on a hot day. It's also related to some A/C cooling effect, but my A/C hasn't worked right since I got the car, so I don't know under what circumstance it turns on then.

I thought that too, but after recently reading Wally's HVAC guide (https://www.928gt.com/t-wallyhvac.aspx), it only comes on when the refrigerant hits a certain temp. He's got some more diagnostics for that fan in there, too.

bureau13

Actually I just found an old thread where that was stated as well...I guess at the very least, if you disconnect your fan from everything you can power it and make sure the fan itself works, then work your way backwards.

Daniel5691

Fuse is OK, going to jumper the sensor next.
Thanks so much.

hwyengr

Driving around the other day reminded me of this thread. I cut the belt to disable the air pump and was driving the car before getting a small 21" fan belt installed.

The electric fan finally turned on for the first time. I thought it was cool enough outside, but enough stop-and-go city traffic pushed the temp just past the 2nd line.

So if you are hovering just below that line even with the car idling for long periods, the fan won't turn on. Hooray for a healthy cooling system!