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Cooling Fan switch help

1425 Views 8 Replies 4 Participants Last post by  tkoepp
OK, I have read through the various threads and tried to test all that I could. My fan is not coming on when it should, here is what I have tried..

Checked the cooling level, all good

Removed the powdercoat / sanded the ground and reseated it.
Jumpered the fan ground to a known good ground,
Pulled the wiring harness on the switch and jumpered from the bottom of the switch to a good ground... none of the above worked..

I then placed my test wire IN the wiring harness that connects to the switch, then the other end to a good ground and the fan turned on.

So I think that it is a ground issue, but not sure. Could it be a grounding issue further up on the harness? I read that it connects somewhere under the tank?
Thank you in advance for your help
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Tim, when the fan switch senses temperature increase (approximately 208 degrees F), the switch closes completing the circuit to ground activating the fan. I understood you to say that you connected a jumper to the terminal on the fan switch and other end of jumper to ground? That should make the fan run. This temperature switch contacts are normally open and contacts closes when water get hot. Hoping your problems are minor.
I would heat the switch up in a oil bath to 207-216 degrees F. measured with thermometer to see if the switch if working properly. The only way to get the switch to close it's contacts is by heating it. I doubt that the switch isn't grounded as it's threads ground to the raditor when installed. I wouldn't rule it "not grounded" completely out as someone might have insulated the threads with teflon tape or other sealant. I recommend OIL bath in lieu of WATER due to boiling point of water is only 212 degrees and switch might require a few degrees higher. You might want to pull switch and clean threads and reinstall prior to heat testing, your call. Wishing you well.

You know that all the circuit is good except through the switch as the fan activates when you jump from the terminal of temp sw. to ground.
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