Kenworth N14 engine fan runs constant

Well - this is inexperienced thinking, but I have an N14, in a T2000, so -

Yes, you want to sort it out - it's a huge MPG drain.

As I understood, the AC head pressure should trigger it, but not keep it on.

Engine temp should trigger it, though mine runs at 180 solid.

Fan switch solenoid as said before.

@NorthernMechanic ??

 

A '99 likely won't have a computer controling the fan. Too old. Could be a faulty solenoid. Only things that control the fan are high A/C pressure in the high pressure side, engine temperature or the manual fan switch. I would start by checking the fan solenoid. It should not be engaged until one of the above conditions is met.

 

Hard to say without seeing a wiring schematic but if that A/C switch is just a 2 prong switch it may only be used to control the A/C clutch. Intake air temp likely isn't used to control the fan (I've been wrong before though). With your engine shut off but key in the run position (air pressure built to cutout as well) can you spin the fan by hand? Can you hear any noticeable air leaks around the engine area? Particularly around the fan hub and fan solenoid?

 

The way my n14 red top is fan on all the time until air is shoved to it then clutch disengaged.... heres a trick for yeah .. get a air blow nozzle.... take air line off the solenoid and blow air into that line while its running.. see if you can manually shut that fan on and off... were not to sure our clutch is getting weak and will work until gets stuck then no matter how much air u give it still wont release the fan and keeps it spinning...

 

Where is the solenoid mounted?
I wonder if the solenoid is weak, and when it gets to a certain temp its failing. Any way to put a bit of heat to it sitting still?

 

Are you sure the air intake temp controls the fan? I think my cat has a separate water temp sending unit that signals the solenoid that runs the fan. If the fan works ok with the manual switch i would think the solenoid is ok

 

Why cant you plug the computer into the truck and simply see what is commanding the fan to come on.

Engine coolant temp
Intake air temp
A/c high press.

It could be a faulty engine coolant temp sensor out of range. Or the obvious of course, wiring issue.

This is a n14 guys , the fan is commanded by the ecm. Same as a cat or detroit.

 

I hate taking something to the dealer.... unless I am completely stumped...

Which I am almost am to this point atm. lol