Electric Fan Runs After Shutting Off Engine: Where To Start

Truck sat for a while - I only used it sporadically over the winter, but would start, run and stop with no problems.

Today, I took it for a longer highway drive and when a got to work, the fans kept running, which they normally do not do even when the engine is hot. Pulled the fuses, did what I had to do and went back to the truck after a couple of hours. Plugged the fuses back in and the fans started again (both fans).

I have two electric fans both running on their own circuit with a relay and a fuse. My initial guess is a bad ground, bad temp sensor (?) or both relays going bad at once. Do I sound like I am on the right track? Any suggestions?

And now the stupic question: how to I test for a "bad ground." If this run is as short, simple and isolated as I remember, step one might be just to replace the grounds.

Thanks,
Bruce.

I would start with the temp sensor since that's what's controlling the fans.

Stuck relay? Smack the relay with a screwdriver, see if it stops. If do, replace the relay.

Not knowing what your using to control the fans, but I'd switch the relays if they are the same. If you have AC, maybe the one that kicks on for AC has failed and is making both run? If the condition changes, then you've got it.

Again, hard to troubleshoot not knowing the ckt.

Thanks All - this will have to wait to the weekend to troubleshoot. Let the truck sit overnight and replaced the fuses and all was fine. Haven't had the chance to run it and see what happens.

Low coolant level?

That can trick the temp sensors and make the fans come on.

Next time it happens unplug the temp sensor,if that stops it then check the actual temp at the sensor and use some common sense. I very very highly doubt a bad ground, that would be one weird wired circuit to have something stay on from a bad ground. Yea possible,but not likely. Either is both relays going bad at the same time. The way I read your post you are running 2 separate circuits complete to each fan. 2 relays,2 fans but are you using a single temp sensor to trigger both relays. That's the first thing I'd check.

Perhaps a chafed/bare ground wire going to ground, causing them to continue to run?