Yes it is a 3wire fan. After the fan runs o. High for a few seconds and shuts off there is still 14 volts on the low circuit but the fan doesn't run? What makes it come on low? Keep in mind I plugged a known good fan into the connector and it's also not working. Does it need more than 14 volts to run on low?

 

I no longer have access to the circuits as TNTech does but I can guess that you are missing the ground (return signal).

 

If you have power at pin 3 (LOW), then it's likely fan motor internal. The fan has one ground for both speeds.


High pin 1 , Ground pin 2. I can't paste the wiring diagram because of the wiring app format.

 

I plugged in a good fan and it still didn't work. I checked the ground as well. I believe the low is Blue with green stripe.

 

The error code is for the control circuit, not the fan. It's more than likely because of the low speed control voltage being on continually.

This voltage is from the TIPM, so there is most likely a problem with the TIPM or sensor or whatever tells the TIPM to turn the fan on.


Both control inputs to the fan should not be on at the same time. The high speed may be working as it should.


I don't have access to the service manual or wiring diagrams for your truck, so I can't help very much.


The low speed winding of the fan appears to be burned out, maybe because it was continually commanded to be running. Unplug it and check the winding with an ohmmeter connected to pins 2 and 3.


Also, while it's unplugged, check the motor side of the harness connector for 12 volts on pins 2 and 3.


Is this the original fan? I can't explain why a known good fan won't run on low when there is continuous power. Very interesting.

 

Yes, if the original fan. The trick only has 45k miles and I'm the original owner.

What should the ohm reading be?

 

I bet you have the other type of fan then, where the voltages are opposed. It may not be a HIGH/LOW system.

 

Here try this>>>

 

I found a wiring diagram but it shows another run relay in that circuit?

 

Such is my life lol. You'll have to match the wiring diagram with your build.