Help with fans

[Fiction1990]

Car has been sitting overnight, I walked by and the fans were on full blast with key off. I started looking online and found someone said pull fuse 4 and if the fans stay on it's the FCM mine did not stay on when pulling that fuse. The car was cold but could the temp sensor still be causing fans to go on? Or is it more likely that the FCM is bad?

[Mike Tries]

Did you try switching the ignition on to look at the temperature gauge? If the temp sensor is causing it, then it's probably telling the ECU that it's way too hot. Your gauge may reflect that.

Can you plug in a scan tool and see if there are any codes?

Cycling the ignition might also cause it to just stop doing that. Not like that's a good thing, because you'll never find out why it happened, but it might just resolve all on its own that way.

If that doesn't clear it up, maybe unplugging the battery for a bit?

[Fiction1990]

Cycling the ignition does stop it for a while. I haven't hooked up a scanner to it. The battery has been disconnected so it doesn't drain, when I reconnect it, it'll take awhile and then the fans come back on. Didn't think to look at the gauge.

[Ozone510]

Cycling the ignition does stop it for a while. I haven't hooked up a scanner to it. The battery has been disconnected so it doesn't drain, when I reconnect it, it'll take awhile and then the fans come back on. Didn't think to look at the gauge.

Do you want a FCM that I have in my inventory. Functionally worthless. Could make troubleshooting easier?

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[Fiction1990]

Thank you for the offer. I think I'm just going to go to pic a part and grab one that way if it fixes it, I don't have to swap it again and they are less than 20$

[codemode]

It’s probably a relay. If your drains are clogged, more than likely.

[Fiction1990]

I already checked the ecm and such, it's dry.

[Mike Tries]

It’s probably a relay. If your drains are clogged, more than likely.

Oh, like a sticking relay? Maybe it was wet at some point in the past and corroded (or corroded by other means, or just broke) and now it is stuck closed?

[Fiction1990]

Would that make the fans go on as soon as the battery is connected? They don't come on right away, I don't know how long it takes, I just happen to hear them.

[Mike Tries]

Oh yeah, probably. Were you able to scan it or look at the temp gauge?

[Fiction1990]

No not yet. By the time I get home I'm the afternoon it's only about 148* here in Vegas

[Mike Tries]

I was someplace like that for a while. I didn't realize that air on Earth could get to 120 degrees. Then I found out that it, in fact, can get that hot.

Maybe it really is the sensor. If it's that hot (110 degrees or so) outside where the weather sensors are, and your car is parked in the sun on an asphalt lot, it could easily be 170 degrees under the hood or in the cabin. If the sensor has failed somehow, maybe it just thinks the car is overheating.

[codemode]

Would that make the fans go on as soon as the battery is connected? They don't come on right away, I don't know how long it takes, I just happen to hear them.

Absolutely, I’ve seen it happen.

[Fiction1990]

Well I swapped the FCM and the fans kicked on immediately, but I started the car and they haven't come on again. Now on to the next problem