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cooling fan problem
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bufflars12  



Joined: 22 Apr 2006
Posts: 21
Location: ny, 10923

PostPosted: Thu Apr 27, 2006 12:34 pm    Post subject: cooling fan problem Reply with quote

i am having problems with my cooling fans..if i were to hard wire them on with a switch, would the engine run too cold? can i just turn the fan on when the temp gauge gerts past the cent line. if this would be a good idea how would i go about doing this. where should i cut the fan off and wire the switch from? should ibypass the thermostat? any help would be apprecaited.thanks
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gohim  



Joined: 02 Nov 2002
Posts: 4462
Location: Rialto, CA

PostPosted: Thu Apr 27, 2006 1:01 pm    Post subject: Reply with quote

It would help if you posted what model year your car was, and whether it has ac or not.

It would be easier if you fixed your problem with the factory fan wiring then if you were to hack the wiring, and try to remeber to turn the cooling fans on or off at the right time, so you don't overheat and damge the engine.

What exactly is your problem with the cooling fans?
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bufflars12  



Joined: 22 Apr 2006
Posts: 21
Location: ny, 10923

PostPosted: Thu Apr 27, 2006 1:03 pm    Post subject: Reply with quote

its an 84 944 with a/c. it seems that the drive fan doesnt kick on. could it just be the thermostat?
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Lizard  



Joined: 03 Nov 2002
Posts: 9379
Location: Abbotsford BC. Canada

PostPosted: Thu Apr 27, 2006 1:24 pm    Post subject: Reply with quote

running the fans constant will not cause the engine to run too cold, but it would be a waste of energy,

as per the fan first verify that with the ign on you are getting a + 12 volts to one of the connectors for the fan. you then need to find the temp sensor in the rad and pull the connectors off it and bridge them together and see if the fan runs,

the two options if the fan doesnt come on when running but by bridging the wires it does is #1 temp switch in rad is cooked, #2 is rad is not opening to allow enough fluid through.
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gohim  



Joined: 02 Nov 2002
Posts: 4462
Location: Rialto, CA

PostPosted: Thu Apr 27, 2006 1:50 pm    Post subject: Reply with quote

The cooling fans should go on whenever the temperature designated by the cooling fan switch (located in the radiator) is reached, and cut-off when the coolant temperature drops down to designated temper (7-10 degrees lower than the "turn on" temperature).

If the temperature switch in the radiator is defective, the fans could be on all the time, or never go one. There are also two relays that affect the operation of the cooling fans. One is the cooling fan relay, and the other is the ac relay. When the ac is turned on, then the cooling fans will continue to run, regardless of the temperature.

If either of the relays is defective, the cooling fans may not function, or may be stuck on.

On a 84 944, you should have a cooling fan relay with two wires on it. Short the two wires together with a sturdy screwdrivers with the ignition off, and the fans should both run at the low speed. If you short the two wires together with the ignition on, then the fans should run at the high speed.

If the cooling fans will not activate with the ignition on or off, with the wires shorted, then you probably have a blown fuse or bad wiring. If the fans will run at the low speed with the ignition off, but not with the ignition on, then the cooling fan relay is probably bad. If the cooling fans will run at the high speed with the ignition on and the ac on, but will not run with the ignition on and the radiator (thermofan) switch shorted, then the cooling fan relay is probably defective. If the cooling fans run at the low speed with the ignition on, the ac off, anf the radiator switch shorted, then the cooling fan relay is probably defective. If the cooling fans will run at high speed with the radiator switch shorted, and the ignition on, and when the ignition is on, and the ac is on, but will not run at low speed with the radiator switch shorted, and the ignition off, then the round resistor located behind the dashboard on the driver's (left) side is probably defective (or the wiring to it is defective).

Note, depending on which fan switch you have, the fans could be switched on anywhere between 160 F and 200 F during normal operation.


Last edited by gohim on Thu Apr 27, 2006 1:53 pm; edited 1 time in total
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bufflars12  



Joined: 22 Apr 2006
Posts: 21
Location: ny, 10923

PostPosted: Thu Apr 27, 2006 1:51 pm    Post subject: Reply with quote

thanks man. i will try this tomorrw and see how it goes
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Stampedetrail  



Joined: 29 May 2005
Posts: 274
Location: Fairbanks, Alaska

PostPosted: Thu Apr 27, 2006 6:53 pm    Post subject: Re: cooling fan problem Reply with quote

bufflars12 wrote:
i am having problems with my cooling fans..if i were to hard wire them on with a switch, would the engine run too cold? can i just turn the fan on when the temp gauge gerts past the cent line. if this would be a good idea how would i go about doing this. where should i cut the fan off and wire the switch from? should ibypass the thermostat? any help would be apprecaited.thanks


When my temp sensor lead broke off, I connected the two leads together that otherwise go to the temp switch (at the radiator, on the driver's side), because I wasn't sure if the temp switch worked or not. The fans ran all the time when the ign switch was on. It doesn't change the temperature of the engine at all, since its temp is controlled with the thermostat. It was just a safety precaution. When I fixed the temp sensor lead, I reconnected the temp switch. If you're iffy about your temp switch, by all means hotwire your fan by connecting the two leads together until you can test your temp switch.
Test the temp switch with a multimeter & with the temp switch sitting in a pot of boiling water & a meat thermometer.
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gohim  



Joined: 02 Nov 2002
Posts: 4462
Location: Rialto, CA

PostPosted: Fri Apr 28, 2006 12:36 am    Post subject: Reply with quote

Making a fixed connection between the two leads that are normally attached to the thermofan switch is a BAD IDEA. Yeah, the cooling fans will run alright. They will run whether the ignition is on or not (at high speed when the ignition is on and at low speed when the ignition is off). The only time that the fans would not be running is if the low speed sooling fan resistor is disconnected, or burned-out, or if the battery is FLAT.

The thermostat controls whether coolant flows through the engine. The thermofan switch controls whether the radiator gets the additional cooling air flowing through the radiator. You better believe that the cooling fans will affect the temperature of the coolant. Without proper operation of the cooling fans your engine is going to overheat whether the thermostat works or not.


Last edited by gohim on Sat Apr 29, 2006 6:03 am; edited 1 time in total
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bufflars12  



Joined: 22 Apr 2006
Posts: 21
Location: ny, 10923

PostPosted: Fri Apr 28, 2006 12:44 am    Post subject: Reply with quote

ok the a/c fan goes on when then a/c is turned on. i have yet to see the driver side fan kick on (but havent really been driving it). i am going to check the relay today
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Ozzie  



Joined: 12 Mar 2005
Posts: 4398
Location: Townsville, Qld. Australia

PostPosted: Fri Apr 28, 2006 5:27 pm    Post subject: Reply with quote

bufflars12 wrote:
ok the a/c fan goes on when then a/c is turned on. i have yet to see the driver side fan kick on (but havent really been driving it). i am going to check the relay today


The ac fan is operating normally.
If you join the two wires on the radiator temp switch the other fan should kick on slowly.
Turn the key on and it should run at full speed.
Let us know the results.

If the fan doesn't work at all hook up 12v directly to it and see if it runs.
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Stampedetrail  



Joined: 29 May 2005
Posts: 274
Location: Fairbanks, Alaska

PostPosted: Fri Apr 28, 2006 7:09 pm    Post subject: Reply with quote

gohim wrote:
Making a fixed connection between the two leads that are normally attached to the thermofan switch is a BAD IDEA. Yeah, the cooling fans will run alright. They will run whether the ignition is on or not (at high speed when the ignition is on and at low speed when the ignition is off). The only time that the fans would not be running is if the low speed sooling fan resistor is disconnected, or burned-out, or if the battery is FLAT.

Not so on mine, for whatever reason, they only ran when ignition was on. You could of course wire from accessories lead if you had to. Until you get another thermofan switch. Just a thought.
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Ozzie  



Joined: 12 Mar 2005
Posts: 4398
Location: Townsville, Qld. Australia

PostPosted: Sat Apr 29, 2006 12:22 am    Post subject: Reply with quote

Stampedetrail wrote:

Not so on mine, for whatever reason, they only ran when ignition was on. You could of course wire from accessories lead if you had to.


My fan used to come on only with the key and on full.
The PO had bypassed the thermo switch and cut the wire to the resistor.
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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
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bufflars12  



Joined: 22 Apr 2006
Posts: 21
Location: ny, 10923

PostPosted: Sat Apr 29, 2006 12:31 am    Post subject: fans` Reply with quote

i took the fans out on wendsay and tested both. one ran 100% but the other one was alittle stiff. i broke it loose and they both spin freely when connected to an external 12v source. so its not the fan motors. i am going to connoct the two wires at the switch today and see what happens. thansk guys
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gohim  



Joined: 02 Nov 2002
Posts: 4462
Location: Rialto, CA

PostPosted: Sat Apr 29, 2006 5:59 am    Post subject: Reply with quote

Both cooling fans should run when the ac is turned on and the ignition is on (not just the secondary cooling fan). I suspect that you have at least (1) bad relay.
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D Hook  



Joined: 03 Nov 2002
Posts: 3092
Location: Omaha, NE

PostPosted: Mon May 01, 2006 1:30 am    Post subject: Reply with quote

If you need a new thermo switch for the radiator, this is the cheapest I've ever found:

http://cgi.ebay.com/ebaymotors/Porsche-924-928-944-Cooling-Fan-Switch-NEW-German_W0QQcmdZViewItemQQcategoryZ33600QQitemZ8061127555QQrdZ1

No relation to the seller. Just passing on my own experience. Cheap and quick to ship. I bought to have a spare. May buy another one.
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