Yesterday it was 90* and humid where I live. I took my truck to the store and left it running with the AC on high. When I came back to the truck, the temp gage was reading 240* or so. After I got moving again it came right back down to 195*.

I came home and popped the hood with the truck still running. With the A/C off (switched on but compressor not running), both fans ran on low, as it should. When the compressor kicked on, (1) fan would come on high and the other fan seemed to spin about 50% slower than the low setting. Once the A/C compressor shut off, they both would go to low.

Per Nelson's website, they should both come on high if the PCM is calling for fans as well as when the A/C is on.

Could anyone help?

 

pm FarmTruc

 

bypass harness and apply 12volts to the questionable efan.
if it turns on hispeed, it's good.
if it appears it's half the speed it should be, it's probably the efan motor.
compare to the other fan to ensure it's operation.

if all is good with the fans, check the relays, be sure they are working correctly. check the terminals for corrosion.

fyi, since your truck is an '04, you can repin that harness so that the fans operate based on ect and ac line pressure.
our new efan harnesses are now equipped with delphi waterproof relays and housings.

 

Both fans work as they should. Each will run on low as they should and each will run on high, just not through the harness. I am beginning to suspect one of the relay's is bad. Does anyone have a P/N for NAPA that I could pick one up?

 

clean the terminals and any 5 pin 40amp relay will do.

 

You can get the relays at any autoparts store off the shelf