Auto fan randomly working in 379 with Detroit 60

I've got a 99 379 with a detroit series 60. Engine fan works great if I use the manual switch, doesn't seem to work 3/4 of the time automatically though based on temperature. Is this an easy fix or am I going to be checking wire continuity?

 

Try a new fan switch solenoid. They tend to act up a little before they fail. When they fail your fan will be stuck on.

 

Would a failing one work every time with the dash switch and rarely with the temp based ecm signal though?

 

Mine did..until it didn’t. Lol, I hit the manual switch and that’s when it decided it didn’t want to shut off anymore. Mine acted up about two days before it completely failed.

New solenoid should be somewhat inexpensive. Had mine replaced at Kenworth and it was $150.00 parts and labor.

 

Huh, alright. I appreciate it. Maybe I can pick up one along the way back home tomorrow. I haven't even looked at where it's at but I figure it should be easy enough to find.

 

I'm not sure on a Detroit but on a cat the fan comes on for engine water temp at 217 degrees. Not any sooner, at least for water temp. So are you surenits getting warm enough to kick the fan on? Factory temp gauges in Pete's are notorious for being inaccurate

 

On my Kenworth it was located on the firewall, left side. I’m sure if you go pick one up they can tell you where it’s located.

 

Yup, I have had the water temp alarm come on a few times without the fan coming on at all. I've read a few places that between 207-210 it should come on in a detroit but it seems completely random when it works.

 

I should also say, the fan comes on every few mins when at high idle. Just doesn't always seem to work while driving.

 

Again I'm not familiar with a Detroit but a cat has one sensor for the gauge and another for the ecm. Possible sensor for fan control one ecm isn't reading correctly or bad connection in harness.