Electric Fan Wiring Troubles

[Robert M Mrozek]

I have a 70 Camaro. Installed a Proform electric fan with a proform wiring kit with a radiator probe temp sensor about 3 yrs ago. Last year the fan started to turn on immediately with accessory ACC power. It is supposed to turn on when it hits a certain temp as measured by the probe and not with ACC ON (at least I dont think so). I also have an override switch installed. I have been trouble shooting for a few days on why the fan turns on with ACC ON and thought I found a short in the wires going to the fan (the power splice was touching the ground splice and it was overheated and melting the heat shrink). When I separated those wires, everything worked fine. Turned the key to ACC ON, fan is static (good), turn on/off override switch...no problems. I rewired the power and ground to the fan and ran a test and the problem returned...the fan started immediately with accessory ON. I then disconnected the temp probe (it comes with a small inline connector) and the fan stops. I reconnect the temp probe and the fan remains static...I figured it would start up again. I then, with temp probe still connected, cycle the ignition from ON to ACC and the fan starts to run immediately again and stays that way with subsequent cycling. I also disconnected the override switch and confirmed it doesnt influence anything. I wonder if I have a bad probe or maybe control module....I checked the probe wire and no damage. But if the probe or probe wire was bad...why wouldn't the fan run when probe connected, stop when disconnected, and run when connected back? I am perplexed. Hopefully i explained in enough details that someone could give me some advice or suggestions on what to test or measure. Thanks in advance. - Rob

 

[Twisted_Metal]

I’m thinking it’s one of two things…

Either your relay is sporadically sticking in the closed circuit position or the temp probe is defective.

 

[Ratty_81]

I replaced an air temp style controller with a much simpler water temp unit and never looked back.
Guessing the probe is bad or controller is bad due to the fan output being shorted to ground.

 

[Gamma454]

I would say module shorted with wires touching. If you ran a simple relay with no controller and use temp probe to ground relay . See if that works

 

[Gamma454]

Simple

 

[73standard]

When fan is running (when it's not supposed to), measure resistance from temp probe to ground. If it's small resistance to ground the probe is faulty. If it's an open circuit the probe should be fine. You might have to verify with the probe disconnected from the rest of the circuit in case there is a short to ground somewhere else.

I'm guessing your shorted wires situation damaged something and now there's a new intermittent path to ground.

Alternatively, replace the probe ground connection with your override switch. If it ever comes on with the override off, then the probe is not at fault or at least isn't the only problem.

 

[COPO]

I would have fused the ign/acc wire from day 1.

 

[Robert M Mrozek]

Thanks to all for all the advice. Helped out a lot. After trying all the troubleshooting advice from this forum, the last thing I replaced in the circuit was the controller and that ended up being the bad part. I think the short I had in the system fried the controller. I used the Proform Adjustable Electric Fan Controllers 69599 and just ordered a replacement.

 

[Chris Greenley]

Thanks to all for all the advice. Helped out a lot. After trying all the troubleshooting advice from this forum, the last thing I replaced in the circuit was the controller and that ended up being the bad part. I think the short I had in the system fried the controller. I used the Proform Adjustable Electric Fan Controllers 69599 and just ordered a replacement.

If that one also fails Try a Davis Craig controller just installed one and very pleased you can set it at any temperature you want for it to turn on and it turns fan #1 on and then seconds later Fan#2 turns on with less stress on the alternator

 

[Gary S]

Electronic stuff will never be as reliable as a simple mechanical fan. If you can find the best controller and sensors, it should work for a long time again.