Does anyone have a diagram of a harness to build it yourself? Do you just wire them right to the PCM or do you have to wire in relays and such?

 

You need three relays. Here is the diagram

 

Sweet, thanks! Now I'm off to try and find relays. Anyone know a good place to get them and what amp relays?

 

you should be able to get them at any god parts store. Look for at least a 30 Amp relay. And it need to be the five pin relays. i dont know the actual name.

 

Bump an old thread.

I cant get my 99 PCM to control my fans on their own with the Nelson Fan harness plugged into Pin 42.

With the stock tune, they are always off. With an aftermarket tune I purchased...the tuner could not get the PCM to shut them off (They were always on no matter what temp he tried)

What settings in the PCM need to be changed so they work?

 

MCM or Mouser Electronics sells the 30A and 40A versions.
Parts Express too. They also have the Relay pigtails for a few bux.

 

There are issues with the older truck PCMs controlling the fans correctly. This thread may enlighten you a little... https://www.performancetrucks.net/fo...d.php?t=465926.

 

Thanks for the link. Looks like more trouble than what it's worth.
I'll mention it to my tuner, but until then I'll just use my Painless thermal switch in the head.

 

I've been running my 05 efans for over 5 years with no issues...I have an 02 PCM though which may make a difference. Only problem that I have had was 2 of the 3 relays going bad after I got the truck running after sitting with a blown trans for 18 months. 3 new 20/30 Bosch 5 pin relays and it's been good since May, using the AC all summer long

 

Mine work great, just change the fan settings in the tune. I just copied stock fan settings from a random stock tune with e fans.