Hello everybody, I have a 2003 Yukon SLT. I recently installed my Blackbear 91 tune along with my brand new Blackbear dual pin fan harness and brand new dorman electric fans. After getting everything installed, I can't get the fans to cut on at all. When I cut on the AC the fans won't do anything. Today drove the truck for a 1/2 hour and let it sit for 1/2 hour and the temperature gauge finally went past 210 degrees and the fans would not come on. I checked the blue 42 pin and the green 33 pin twice and made sure that they were in the right slots and that they were seated properly. I even attempted to push the pins back out the slots and they would not go up. I triple checked my positive and negative wires. I also hooked the fans up to my battery to make sure they would come on and both fans worked. I don't know anything about relays, so I don't know how to check and see if they are good or bad. I'm thinking either the pins are not turned on or I have a bad relay or relays. I'm all out of ideas, any suggestions on what else I could check would be greatly appreciated.

 

You can try unplugging the PCM connector and ground pin 42 and 33 with a spare piece of wire, and the fans should come on. I have the same issue on mine. Everything is installed correctly, fans work when pin 42 is grounded, but they never come on with the PCM. I'm fairly certain Nelson never actually turned them on in my PCM. Their fan harness was also missing the relays when they sent it to me.

 

That's what Justin told me to do and it did work however Justin said that the fans are turned on in my tune. I'm waiting to hear back from him to find out what I should do next.

 

Sounds like we're in the same boat. Let me know what he says.

 

You can wire in two switches spliced into the wkres goin to pin 33 and 42.
On your switches, run a ground wire to one side of the switch. The other side of the switch your gonna run to one of the wires goin to pin 33 and another switch and wire running to wire on pin 42.

That will let your fans work till you get figured out whats wrong.


If you can ground pin 33 and ground pin 42 and the fans come on, then odds are you have a pcm problem, whether tune or other problem.

 

Justin automatically turns on E-fans in all of his tunes. Tested the fuse?

 

PCm file must be set up fan options as Ac recirc door and not 2 fan setting. If you turn key on to run position and ground the green and then the blue wires each should turn on independently.

 

Ever find the problem or problems? Would like to know what was the result... I'm in the middle of the same install myself.

 

When I did my fans it was in the middle of November,didn't really get a chance to see em work till may and when I was using the AC this summer,the stock cooling system does a really good job I think.

 

I found my issue, which was that Nelson never actually turned on the fans in the PCM they sent me