Fan won't stop spinning help!!!!

I wouldn't just go changing parts and throwing money at it. Figure out how it's wired and diagnose the issue.

 

I take it this is probably a Detroit? The fan solenoid should always have power on one wire, the ECM controls the ground. Are you also having trouble with an intermittent Jake as well?

The gasket on the back cover of the ECM may have failed, allowing it to fill up with water. All of the transistors that control grounds for various things, like the fan solenoid, are located on the bottom of the ECM board when viewed as it is mounted on the motor. They are first to corrode when the case gets water in it.

If you can ground the fan solenoid wire and get the fan to operate, I'd suspect a flaky ECM or broken wire to the ECM.

 

Im intrigued with this issue. Of all the fans in my life I never had noticed anyone that refused to stop, in any event I relied on 24/7 fan going anyway. It was more of a potential issue if the fan actually stopped out of the ordinary.

I will have to do some thinking about this some more.

 

It's really a common issue. Most fan clutches these days use air to release them. This way, if there are any problems, the fan will stay on rather than not work at all. The old air engage fans used to be the opposite, if you had a air, solenoid, or wiring issue, the fan would not come on at all. Back then, many came with bolts to cage the fan on to get you home. That's going back 15-20 years now. These days, most fan problems (other than the clutch itself failing) will make the fan run all the time.

 

Probably a bad transistor on the Fan Control #1. You can have the fan reprogrammed to another output but the others are probably not far behind.

First verify continuity on the ground wire all the way to the ECM. Check that the connector is not corroded.

If all is good with the wire and connector, pull the ECM, remove the back cover and inspect for water infiltration and corrosion. Use polyurethane sealant to seal it back up if you don't find anything obvious. It's probably just a dead transistor. Have it reprogrammed to another output.

If it is as I suspect--water damage, then replace the ECM.

 

Lets not throw the towel in and assume you need an ECM just yet. Do like he said, trace the ground wire back. Any open in that wire will keep the fan running. Once you're sure that all the wiring is good, then you can worry about an ECM issue.