I am trying to install a manual override switch for the engine fan on a 2008 freightliner columbia with a series 60 detroit. can anyone tell me where to hook in. any help would be appreciated.

Trying to figure the same thing out myself.

I am trying to get confirmation how my 07 century with a ddec v is wired. Freightliner dealer is not much help in giving up wiring diagrams. I was told the solenoid is ecm co trolled and that you are actually sending a signal to the ddec ecm.

But that's as far as I've gotten so far. Service writer said he'd look into it and that's as far as I've gotten with it.

Getting an older truck with a mechanical engine is looking more and more favorable to me.

When my temp sender went bad it turned the fan on all the time. I was told when the ecm doesn't get a signal from the sender it turns the fan on to be safe.

That would lend credence to what they were telling me.


The techs understanding is that the fan switch gives a signal to the ecm. He didn't know if it was a ground signal or a 12 v signal. Nor did he know what pin it was to.

I do a lot of work in the mountains and I want to be able to turn the fan on when I start the pull so it doesnt keep coming on and off. I comes on at 210 and keeps climbing 10 degrees before it starts to come down. It turns off at 200 so it is on and off while I am climbing. Just trying to make it easier on the fan clutch.

thanx for the replies.