924Board.org

[Tom_15]

A while back I noticed that whenever I turn the key to the on position (car still off). My rad fan kicks in full bore, even if I haven't had the engine started in days and I know it's cold.

Is my thermostat or thermo-switch blown? (if so are they generic parts I can get at the local parts store or do I gotta order in)
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1978 924 N/A 4-Sp.

[Chrenan]

Probably the thermo fan switch which screws into the upper driver side of the radiator.

There are a couple of temperature ranges for the switch, make sure you match it to your thermostat temperature range. Probably good to replace your thermostat at the same time.

Both parts may very well be available at your local auto parts store. I don't have the patience to deal with all the hassle of trying to get Porsche parts through a local place so I usually just order online.
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1987 951 - M193 Version for Japan

[Tom_15]

I'll pop it out then and do the haynes temp test when I can get my hands on a large enough wrench
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1978 924 N/A 4-Sp.

[Ozzie]

If the rad temp switch is stuffed the fan should run at slow speed when the ign is off.
Unless the resistor is removed from the circuit, (previous owner done this to mine).

It sounds like the temp switch. I'd check the cool down circuit with the resistor in it as well.
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[Chrenan]

That would be a shame, the temp switch is much harder to access.
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1987 951 - M193 Version for Japan

[Tom_15]

looks like Ozzie is right. I finally got my hands on a big enough wrench and the thermoswitch performed well in the boiling water test.

Sounds like a fun night tomorrow after work.
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1978 924 N/A 4-Sp.

[Chrenan]

That's too bad Tom, at least you have it narrowed down now.
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1987 951 - M193 Version for Japan