With the use of a LS1 fan how does it operate when used with a nelson wiring harness in regards to (fan cutting on and off) Also are there any tips in the installation of a LS1 fan and nelson wiring harness in a 03 GMC

 

First, you get the PCM tuned to turn the fans on and off at pre-determined temps, depending on your application and what temp t-stat that you're using. (I'm using a 160* stat and my fans are set to come on at 180* and off at 173*). This is done with tuning software such as HPTuners, EfiLive, etc., or by a custom tuner such as PCMforLess, Nelson, etc.

The harness has 3 relays and funcions as follows:

1)Engine reaches turn on temp, both fans come on low
2)Engine reaches turn on temp and AC is on with the compressor running, both fans come on high
3)A/C on with compressor running, engine not up to temp, 1 fan on high.

Installation is straight forward and a piece of cake...biggest problem folks seem to have is getting the wire/pin completely seated into the PCM connector...you just have to carefully push it in and make sure it "clicks", then check that it is as deep in the connector as all of the other pins.

My harness has been flawless since day 1

 

Alright, so what will the fans do if your pcm is not tuned? Just wondering cause i'm waiting on getting it tuned after i get my headers on.

 

The fans will do nothing without a tune. You can however, hook up a temporary ground switch to the wire that goes to the pcm and be able to turn them on manually until you get your tune.

 

I ended up usuing a grond switch for both of my fans. I had jesse bubb at wait4me turn on pin 42, but he dident set it to come on at a certain temp so it was always grounded after the truck was turned on. I have 2 switches above my air bag on/off that control each fan. I like to be able to control the fans myself because right now I dont need any fans because its about 2 degrees and i do most all highway driving. But during the summer I might switch it back and disable the interior fan switchs as I will need them, and I might forget to turn them on then get some overheating.... thats no good. Later.