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924S right side cooling fan running with Key off

 
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Birdman 996  



Joined: 13 May 2021
Posts: 3
Location: Georgia USA

PostPosted: Thu May 13, 2021 8:45 am    Post subject: 924S right side cooling fan running with Key off Reply with quote

Having a strange cooling fans issue on my 1988 924S. Went into the garage and the AC cooling fan (passenger side) was running with key off and out of the ignition.
Looking at the wiring diagram and reading other posts and system descriptions I don’t see how this can happen. That fan should only receive 12 volt power with the ignition on. Even if the cooling fan relay is stuck closed or the AC switch is left on or bad, the power source, (G7) on the Clark’s Garage wiring diagram, should not be hot with the ignition off.
Somewhere this fan is getting power. Weirder is that with the ignition on both cooling fans work as designed. However, after the engine is turned off, when the driver’s side fan completes the low speed “cool down” and the thermofan switch opens; the DS fan shuts off normally, BUT the PS fan immediately starts up. I have not verified that the cooling fan relay is closing at that point but it must be. There is no other route to provide power to that fan except through the cooling fan relay pins A to B and fuse #5.
The cooling fan relay has been replaced, and the fresh air relay checks good.
I cannot locate the air conditioning relay. Can anyone steer me to where this might be in the car? It does not appear to be any of relays I – VII in the fuse box area. (although FWIW I don’t see how a stuck closed air conditioner relay can provide unswitched (always hot) power to the PS cooling fan.
To further complicate: we did a partial AC delete 4 weeks prior to the random fan running discovery. We only unplugged and removed the compressor and capped some coolant lines. If this could somehow be related it had a one-month delayed reaction. But…still only a coincidence?
Could use help locating that AIR CONDITIONING RELAY for more troubleshooting, and any other troubleshooting advice.
Thanks, REID
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11670
Location: PacNW

PostPosted: Thu May 13, 2021 11:49 pm    Post subject: Reply with quote

Bad AC relay. #3, to the right of the fuel pump relay.
_________________
Toofah King Bad
  • WeiBe (1987 924S) - 931 S3
  • Red (1987 924S) - Pro44/Spec944
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Birdman 996  



Joined: 13 May 2021
Posts: 3
Location: Georgia USA

PostPosted: Sun May 16, 2021 12:50 am    Post subject: Reply with quote

Thanks for the help.
That relay tested Good. Also the air conditioner relay under the passenger side dash board far right of the AC Blower tested good also.
For some reason the fans relay is closing when the key is off and the engine is cool. I can't figure out how it is getting power with the key off. The 12 volt power supplied to that relay is off when the ignition switch is off.
If I pull the #3 fuse on the "additional fuse panel" it opens the relay. I'll check the resistors next if I can find them.
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Birdman 996  



Joined: 13 May 2021
Posts: 3
Location: Georgia USA

PostPosted: Fri May 28, 2021 9:18 am    Post subject: Reply with quote

We've read several posts that reference defective wiring and connections at the cooling fan resistor(s) that step down voltage for low speed operation of the drivers side fan. On the later 944s these resistors are located on the engine side of the firewall near the battery. However the 924S wiring harness is more 924 than 944 with some modifications for the 2.3L engine and 924S features.
Can anyone tell me if the resistor(s) are located on the aft side of the firewall in front of the glove box? Or where? Also are they disc shaped like the 944?
Lastly, does anyone have the part number or rating for said resistor(s)?
Many Thanks.
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