96 FLD 120 / 12.7 S60 Fan Always On

DDEC 4 is ecm controlled. Take line to fan hub with engine off and blow shop air in. Does it release and spin?

 

Maybe lines on solenoid are backwards?

 

Only rea

But you changed the solenoid.

 

I grasping at straws here. Some fans engage with air, others disengage with air. I prefer the latter. When it goes bad, simply remove the air line and crimp it. Fan stays engaged till it can be repaired. Other way, you have to install a bolt to lock it in place. I’ve had both. I can’t say for sure which one I have now. You definitely have a mystery on your hands. Make sure you got the correct part. Maybe this helps.

 

Then there this. My 2000 ddec 4 has the EDM. It’s located it’s the bottom of the fuse panel in my FLD. Unless I missed something, you never mentioned what make Truck you have. Might help, not all the same. Seems the problems the solenoid or the wiring to it. I can’t understand why it was spinning freely, unless the key was on. Maybe just until it lost air. Then replaced it with wrong part, or hooked up wrong. It’s as if the override switch is constantly on. I’ve hooked up hoses and lines backwards, even when I marked them before. Won’t hurt to double check. Just do 1 thing at a time. Less confusing.

 

Yes, fan should move. I’m sure it will. If not it’s stuck. I’ve heard of hitting with a hammer. But your issue is no air. I’m no expert myself. Been plagued by fans running too much on both my Freightliners. My 99 had a bulletin that required splicing in a harness to re wire the solonoid. It used to engage in winter for no reason. Owned the Truck 4 years before finally finding a Dealer that even heard about it. $50, 10 minute fix. Just never know.