M2 Cooling fan intermetent

[RETIDEPXE]

Sitting at a light, the temp shot up to about 230, eng protect lite on, shut it off, checked under hood, nothing boiling, full of coolant, fan spins freely, belt in place. Got in, pumped brakes to remove air in tanks so to engage horton fan clutch, started up and put it at high idle. Temp came back down to normal.

We are back on the road and the horton used to kick on around 200 degrees, now intermetent. I rebuilt the horton last summer with the upgraded bearings and it is functioning as it should, holding air and comes on when I force the air out by pumping the brakes.

I'm suspecting a fan switch relay problem, can anyone tell me where the relay is located? Found a pic of it online but following the air line goes into a large covered loom under the chassis. ; 2007 M2106 with Cat C9, thank you.

 

[fr8hlr521]

Our 08 with cummins has it on the Drivers side firewall. Do you have a dash switch?

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[RETIDEPXE]

Sorry for delay, stayin busy.

fr8hlr521, thank you for the reply. I don't have a dash switch but have to look into wiring me one up, shouldn't be too hard .

I did learn the photo of the relay I posted above is off of a 2012 M2. My '07 utilizes the sucky AMU's to control the horton fan clutch. I know we've beat the AMU issue to death already. I've never had a problem with the cooling fan solenoid in a million plus miles so can't complain about that one. The brake light AMU and AMU #2 are a different story, at least until I learned to clamp them all together with a carpenters clamp (sounds hooky I know) before tightening up the mounting rail. Really haven't been a problem since.

We were caught in the Windy City stop and go traffic this afternoon and the truck held just below the 200 mark with the A/C on, granted it wasn't that hot outside, horton never kicked in, so not sure if functioning properly or not. No apparent air leaks front to back, so we're keeping an eye on it till we get home to dig into it further. No codes were set as we shut it off quickly when it happened. Happy to report 800 miles since I have no indication of water in oil or oil in water so far.

Last time we were home I did a rather thorough under chassis cleaning with the Royal Purple concentrate and gallons and gallons of water, may had something to do with the it. Also the wife just pulled a hill with 9000#'s in the back before sitting at the red light for some time.

ANy body else had a similar issue are welcome to chime in.

Enjoy the spring weather, life IS a miracle.

 

[Dynamite 1]

Could be the temp sensor on the ac dryer that actuates the fan. Its of course the one with the 2 wire plug on it. Should be the one on the [ R ] side as you are looking at it.