C15 fan on continuous

they may have over pressurized the a/c. making the switches kick on the fan. or it's just a quincedence the fan silinoid went bad also. if they put too much oil in the a/c system the excess can get in the switches and jam up the switches. just had this happen when i blew a a/c line on the road and charged it with those cans you buy in the truckstops.

 

another thing you can try is unplug the high and low pressure switches and unscrew them from the line, then plug the plugs back in leaving the switches hanging loose. and see if fan cycles correctly. you wont loose freon because there is a valve in the fittings that will keep the freon in. another thing to check is the intake temp if it is getting to hot it will tell the ecm to run the fan. learned that one recently!

 

power wash engine by chance and poss sticking the clutch fan .. i was in iowa last summer all the dust bilt up so i washed truck then fan acted up then got worse . so i took the hammer while at idle taped on clutch dirt dust came out and has worked fine. very dangerous

 

I was having the same issue last summer, had compressor replaced, shop drained and refilled freon twice, AC would quit working from time to time, usually when i was sleeping at night. I was waiting to unload one day and decided to do some checking, unplugged the entire harness and checked the pins, one of them was bent. So I just replaced the whole harness. Haven't had any trouble since. I think the harness was 50.00.

Sent from your iPhone via my Galaxy Nexus!

 

It does sound like its an a/c hi pressure switch. things that control fan are 1 coolant temp. 2 intake manifold temp. 3 a/c hi pressure switch. 4 fan override switch.

 

I just had the same problem with my c13. I was getting 13.4 volts and as soon as I hooked up the solenoid it would lose voltage. I just spent 5 hrs trying to figure this out.. I started traking the 12vdc wire and found a corroded wire have way down the harness toward the ECM where the wire harness was zip tide to the back side of the valve cover on the driver side.. How I found it was I did a continuity test on the power wire and pin 21 one the ECM harness. It had no beep so the was broke between each end. So I started probing from one to the other and found the corroded wire along with 5 other wire that was worn thru almost ready to break ... Hope this helps
Catshaker

 

Sorry one minute to late..... It made me ready to set the #### thing on fire!!!!!!

 

dont worry, it's a truck something else will break or wear out and you will have to work on it again!!