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JSilverman
Joined: 16 May 2006
Posts: 93
Location: Burke, VA
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 Posted: Wed Oct 04, 2006 5:58 am Post subject: Fans |
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| The fans in my car do not appear to be functioning properly. The low speed fan does not come on. When the temp guage reaches 3/4 both fans come on in high speed. Both fans also come on with the AC. From reading here and other places the problem could be a bad thermowitch, bad fan relay, bad resistor. I dont really have any way to test stuff. Is there anything I can do besides replacing parts? |
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D Hook
Joined: 02 Nov 2002
Posts: 3158
Location: Omaha, NE
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| Posted: Wed Oct 04, 2006 10:07 am Post subject: |
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You can try a lower temp thermo switch to make the fans come on sooner. Available at Perf. Products.
My understanding is that both fans kick on when triggered by the switch or when the A/C is turned on. Then, if they're still running when the car is shut off, only one fan runs and at a lower speed to cause less drain on the battery. Anyway, that's the way mine work.
I put a lower temp switch on my car and the fans now kick on at just about the half way mark. Much better.
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'80 924 n/a SOLD |
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JSilverman
Joined: 16 May 2006
Posts: 93
Location: Burke, VA
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| Posted: Wed Oct 04, 2006 10:27 am Post subject: |
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| The fans dont stay on after the car is turned off though so I dont know if a lower temp switch will fix it. The low speed fan does not come on when its supposed to. |
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D Hook
Joined: 02 Nov 2002
Posts: 3158
Location: Omaha, NE
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| Posted: Wed Oct 04, 2006 10:32 am Post subject: |
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So if both fans are running and you turn the car off, the low speed one doesn't stay running, correct?
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'80 924 n/a SOLD |
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JSilverman
Joined: 16 May 2006
Posts: 93
Location: Burke, VA
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| Posted: Wed Oct 04, 2006 2:01 pm Post subject: |
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| D Hook wrote: | | So if both fans are running and you turn the car off, the low speed one doesn't stay running, correct? |
Temp reaches the half way mark where the slow fan should turn on. It doesnt. Tmep reaches 3/4 and both fans come on in high speed and the temp comes down to the 1/2 mark or cooler. Both fans come on with the AC. No fans run with the car off. My understanding of the fan system is that the slow speed fan has 2 circuits. When the temp gets to half it opens the circuit passing through a resistor which causes the fan to run in slow speed. When the temp reaches the 3/4 mark a second circuit opens, shorting the resistor and allowing the fans to run in high speed. This tells me that there is possible a problem with the resistor, the fan switch or the fan relay. Im just trying to figure out where to start so I dont have to buy a $150 relay to see if thats the problem. |
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D Hook
Joined: 02 Nov 2002
Posts: 3158
Location: Omaha, NE
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| Posted: Wed Oct 04, 2006 10:52 pm Post subject: |
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Good description of the problem.
My fans don't do that but it may be different on the S model.
Which relay do you need? I've got some extra that came from an early 944.
Good luck!
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'80 924 n/a SOLD |
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JSilverman
Joined: 16 May 2006
Posts: 93
Location: Burke, VA
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| Posted: Wed Oct 04, 2006 10:55 pm Post subject: |
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| Well I just checkd prices and the $150 relay is for late 944s, but its still a $40 relay p/n 944 615 113 01. Its an AC relay. |
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Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
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| Posted: Sat Oct 07, 2006 12:53 am Post subject: |
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Don't bother with the relay. Current flow through the resistor for after shutdown fan running bypasses the relay (have a look at the wiring diagram  ). The problem is probably with the resistor or wiring to/from it. The temp switch might also be bad, but since it's functioning and switching the fans on at some point while running, it should be doing the same after shutdown, so most likely a resistor/wiring problem.
[Actually there are 2 relays involved with fan operation - the "AC relay" and "cooling fan relay". They're both apparently ok since the fans come on when you switch on the AC and they also get switched on by the temp switch.]
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"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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Paul
Joined: 02 Nov 2002
Posts: 9491
Location: Southeast Wisconsin
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| Posted: Sat Oct 07, 2006 8:56 am Post subject: |
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| JSilverman wrote: | | Tmep reaches 3/4 and both fans come on in high speed and the temp comes down to the 1/2 mark or cooler. Both fans come on with the AC. No fans run with the car off. |
Unless your car's radiator temp switch has 3 posts, your car is behaving normally except one fan should run on slow speed if the radiator is hot enough when you shut off the car.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy. |
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JSilverman
Joined: 16 May 2006
Posts: 93
Location: Burke, VA
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| Posted: Sun Oct 08, 2006 2:43 am Post subject: |
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| Im assuming the temp for the slow speed fan is the same as when the high speed fans turn on? |
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Paul
Joined: 02 Nov 2002
Posts: 9491
Location: Southeast Wisconsin
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| Posted: Sun Oct 08, 2006 11:47 am Post subject: |
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The two post radiator temp sender is a simple 1 pole switch, all it does is provide a ground for the fan relay's coil.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy. |
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