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East Coast ISX · 12-17-2019, **(Subject: Help ..Fan has gone Haywire )**

Cruisin westboud on i-70 today, pulling 40000lbs of car bumpers and parts, Clutch fan came on and didnt turn off for almost 20-30 mins , never had this happened to me before, mind you the temperature outside was in the 20s f. Any idea fellas ? After turning off it went back to normal operation, checked fluids and evrything is on point....

Signature620 · 12-17-2019, **(Subject: Help ..Fan has gone Haywire )**

You need to connect to the ECM while it's happening to see if the engine is engaging the fan. There are fault codes, sensors, switches, damaged wiring & a solenoid that can all cause the fan to engage.

It is common for the AC pressure switch or it's wiring to cause the fan to come in for no reason.

Mattman · 12-17-2019, **(Subject: Help ..Fan has gone Haywire )**

Was the defrost on when this happened?

Chamberpains · 12-17-2019, **(Subject: Help ..Fan has gone Haywire )**

At 20°f the a/c or defrost shouldn't naturally turn the fan on. Especially if the truck is moving.

Signature620 has the right approach. You need to know what switch, fan solenoid or temp sensor was commanding the fan on. Also inspect the fan hub for air leaks or mechanical problems like a bearing starting to fail.

tree98 · 12-17-2019, **(Subject: Help ..Fan has gone Haywire )**

(12-17-2019 )Signature620 Wrote: You need to connect to the ECM while it's happening to see if the engine is engaging the fan.

Can this be seen in insite?

Rawze · 12-17-2019, **(Subject: Help ..Fan has gone Haywire )**

LOL ... mine did this last week... My fan-clutch is pouring air out of it (bad seal), allowing it to re-engage for 30 min, sometimes hour or 2 and go off again.

I do not have a fancy engine fan light in the dash though.

Check to see if the ECM is turning it on, and why, or perhaps if the thing is pissing air.

Just another possibility / consideration.

Mattman · 12-17-2019, **(Subject: Help ..Fan has gone Haywire )**

Paccar likes to turn the fan on when a/c compressor comes on. If on defrost a/c compressor will cycle on and off. Now should the fan have stayed on, no. Just saying a/c pressure switch can stick causing fan to stay on.
From your gauges truck hasn't warmed up yet so doubtful it is coolant temp related.

Nostalgic · 12-17-2019, **(Subject: Help ..Fan has gone Haywire )**

Ironic. I had this issue today - fan came on for no reason. My fan idler bearing is shot. It must have wobbled enough to lock in the clutch for a little bit. Hoping I can make it home tomorrow leaving fan engaged. Brand new Kit Master too - it’s getting a new Horton and Kit Masters is on my junk list.

JMBT · 12-17-2019, **(Subject: Help ..Fan has gone Haywire )**

That’s weird I have had great luck with Kit Masters. I rebuilt mine, bearings and all with one of their kits a couple years ago and no problems since.

Anyway I agree with Mattman, fan on my Volvo cycles anytime AC compressor is on including defrost (regardless of outside temp, and moving or not) as pressure builds in the refrigerant system.