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Re: Cooling fan issue

Posted: Tue Jun 24, 2025 5:09 pm
by BennSport
Okay the thermoswitch is a little harder to access than I thought. I’ll check it later this week when I have the car jacked up to recharge the ac

Re: Cooling fan issue

Posted: Wed Jun 25, 2025 6:37 am
by walfreyydo
Check the fan relay first before doing the thermo switch. Its much easier to access and test.

You just unplug the connector that runs from the thermo switch to the relay, and then probe/jump the contacts in the relay connector to manually activate the high and low speed fans. If they work as intended when jumpered, then its likely the thermo temp switch. Again, outlined in Clarks.

Re: Cooling fan issue

Posted: Wed Jun 25, 2025 6:25 pm
by BennSport
So jump terminals 85 and 86 on the fuse block correct? The Clark’s page doesn’t say anything about bypassing the relay to test

Re: Cooling fan issue

Posted: Wed Jun 25, 2025 6:37 pm
by BennSport
Just tried removing the fan relay and I don’t have enough access. It’s so tucked away and the fuse block is too hung up for me to remove it to gain clearance. Aside from removing the bottom right screw and moving it past the hook are there any additional steps to removing the fuse block?

Re: Cooling fan issue

Posted: Thu Jun 26, 2025 6:52 am
by walfreyydo
Clarks says you should also be taking resistance readings (in addition to running 12v across 85 and 86) so would recommend following that procedure exactly.

I am only familiar with the later model cars, which you can test/jump the pins on the actual connector for the thermo fan switch which leads to the relay, while also having a more accessible fuse panel under the hood.

I dont know much about the early cars and how to remove the fan relay from the fuse block, unfortunately, so I dont have any tips for you. Maybe others will chime in with a good technique to removing that fan relay.

Re: Cooling fan issue

Posted: Thu Jun 26, 2025 8:20 pm
by 944er
Easy check if you have A/C. Turn on the A/C. If the fans both come on, it is the thermo switch in the radiator, or the wiring going to it.

Re: Cooling fan issue

Posted: Sun Jun 29, 2025 10:20 am
by BennSport
Yes, the fans do kick on when I turn the A/C on. I bypassed/jumped the thermofan switch, and everything seemed normal. 1 fan turned on in low speed while the car was turned off, and both fans kicked on in high speed with the car on. I went digging around a little and noticed the leak is actually coming from the thermoswitch. I’m planning on replacing the gasket and thinking I should just buy a new switch while I’m in there. I just don’t know what temperature variant to order with the thermostat I have in the car. I’m also thinking about replacing the radiator drain plug with the Lindsey racing radiator drain kit and was wondering if anyone has anything to say about it.

Re: Cooling fan issue

Posted: Sun Jun 29, 2025 10:59 am
by 944er
So the thermoswitch is bad. Part number 823 959 481 F

Re: Cooling fan issue

Posted: Tue Jul 01, 2025 12:05 pm
by icb
I purchased the remote drain a couple of years ago but haven't installed it yet, I'm waiting till I need to drain the cooling system again. I wrote about it here :
https://icb-machinations.blogspot.com/2 ... n.html?m=1

Re: Cooling fan issue

Posted: Tue Jul 01, 2025 12:37 pm
by Tom
I like having a drain valve in lieu of the blue plastic plug, but I made my own from McMaster parts. I didn't see any point in having a big floppy hose attached to the drain. Mine has a valve with barb on it, so when it's time to drain, I can slip a hose on the barb and open the valve. Seem tidier and less prone to inadvertent leaks that way...