Cat Cooling Fan Issues...Again

Cat coolant temp sensor.located on fron.t side of the thermastat housing.35 bucks or so for sensor.it could also be the high pressure ac fan switch.find high pressure ac fan switch bypass the switch.unplug and put paperclip inside.and drive around and see if problems continues.the coolant temp switch will show erratic voltage when you put it on the computer.

 

I had a similar prob, turned out to be a bad elec ground.

 

3 mins on and then off is the same default program timing for the fan when the ecm sees A/C high pressure switch input. That should be the red one near or at the compressor. Try to unplug it and see if the fan stays released. The coolant temp sensor that is read by the ecm to control the fan also sends the data to your coolant temp gauge. If the gauge is reading normal the sensor and wiring should be fine. (The insulation needs to be fixed for sure!)

 

i think u said this was in a international?my cats is in a pete so it uses two seperate coolant sensors.One cat sensor for the ecm on the front side of t stat housing and one on top of housing for the gauge in dash (mechanical gage).So if your temp isn't jumping around more then likely its the high pressure ac fan switch, if you just unplug the ac switch the fan will run steady.unplug the harness and jump the harness with paperclip or wire and see if problem continues.

 

Jumpering the high pressure harness will work but he'll have to stay on top of using the fan manually as needed if he does. I did that and thought it was a bad high pressure switch. Turned out the harness that connected to the high press switch was making poor contact. If he could put a zip tie around it real tight somehow just to see if the connection improves while it's plugged in, and the fan shuts off - get a new harness. Using a paperclip will wallow out where the contacts were made - somebody on here pointed me in this direction when I had a similar problem and they were right on. My fan never would shut off though.

 

I just went through this.i jumped my ac switch and it was still doin it.so when we put it on the cat computer it was showing eratic voltage for the cat sensor.sometimes the sensor loses its ground.the cat sensor grounds itself to the tstat housing.make sure if it is the sensor and u change yourself torque it to the proper specs.