Fan stuck (Cummins isx)

Can we expand on "simple problem ".

Mine sticks sometimes for 20 or 25 minutes, and always when I'm leaving, never when it's rolling.

The big problem I see, besides it making it suck fuel, is that it keeps the engine right at 175 or so, and doesn't allow it to cook up the DPF.

 

Is you A/C working properly? Other than main engine issues I've normally seen high pressure switches keep your rad fan on.On a second note please keep the DPF hot and get cleaned every 250k

 

By high pressure, high limit switch, you mean fan clutch solenoid?

 

He means AC fan switch. High side pressure switch that cycles the engine fan during AC operation. This is always and input to the ECM to tell the fan to come on during AC demand. Intermittent connections or opens in the switch or wiring can cause intermittent fan operation or the fan to run continuously. Not always, but usually a normally closed switch that opens when High side pressure reaches a preset pressure.

 

A decent shop would know how to check said switch, and associated wiring yes? Not Freightliner lol, won't go there.

 

Yes indeed. Monitor switch state in the ECM is the easiest way. Biggest challenge I face is tracking it down when it only does it sometimes. Intermittents can be a real bugger. Much easier to fix it when its broke good. LOL

 

That's what my wrench said. He's like "Dude you need to let it get a lot worse."

 

I'm going to try starting out with the AC off and see if that makes a difference. This morning I left with it off and the fan worked perfectly.

 

Dave,
Here is what I would do. If you can, hook up a set of manifold gauges to the AC ports. If you don't have a set, borrow them or they can be had for cheap at Harbor freight.

A/C R134A Manifold Gauge Set

Monitor the high side pressure and note what the pressure is when the fan comes on and cuts off after the pressure comes down. I forgot what truck you have but call parts dept and see if they can give you the specs for the switch on and off pressures. Might be worth tossing a switch at it to see if anything changes. I assume that the AC performance is acceptable given your location, have you had the charge amount checked anytime recently? Maybe overfilled? Just thinking out loud....

Good Luck

 

Does your fan clutch look like it's 20 years old? How many miles on the truck? The clutch is about $450(no core), takes about an hour to replace. Mine went at 560K probably got lucky it lasted that long.