944 cooling fans

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studog

Original Poster:

268 posts

258 months

Monday 17th July 2006
quotequote all
I have been through the Clark's garage trouble shoot for the relays on my 89 S2 but none of the symptoms match my problems.
The car starts fine and runs up to tempreature, just above the first mark so about 82 deg. When it heats up in traffic the fans come on at slow speed and drop the temp, all good. the problem is that they then do not turn off regardless of the temp of the rad or engine.
Disconnecting the temp switch makes no difference. If I pull the relay it clicks off as I pull it out and clicks back on as I plug it back in. The contacts all move fine. The leads from the switched side of the temp sender are now running to ground either so it is not that.
Turning off the ignition will kill the fans but as soon as I switch back on they are running. If I leave the car over night then the process starts again with the fans being off until the first time they are needed when they will stay on again.
The car does not have AC.
Any other pointers before I spen £100 on a new relay?

studog

Original Poster:

268 posts

258 months

Monday 17th July 2006
quotequote all
Thanks for that. The thing that worries me is that the fan behavior has changed. I think the relay must have a timer circuit in it as the earth from the rad disappers as soon as the temp drops below 92 deg and the fan is supposed to run until 80. There is no other temp sensing involved. I guess it is a new relay all the wiring checks out fine.

As to the plate on my Seven. The plate style is legal on an up to 1973 car as it counts as white on black sort of. It is a 1975 reg and no copper or MOT guy has spotted the difference (yet). I've manged 6 years with it so far. Strangely I got a ticking off about a small one on the Porsche in 3 months, they spotted it in the dark too!

studog

Original Poster:

268 posts

258 months

Wednesday 19th July 2006
quotequote all
Thanks for the offer Paul. I'm in Herefordshire so bit of trek
away from you. It all points to the relay so I think I will just order one.
I don't mind buying parts I just like to understand the problem before commiting.
I guess I ahve been bitten by too many garages swapping stuff just to see. It does puzzle
me why they felt the need to make it so complicated. If you take cover off the relay there
are four seperate relays and a chip in there!