Yep, then Nelson harness works as follows:

PCM (temp) trigger only - both fans on low
A/C trigger only - one fan on high, one fan off
PCM and A/C trigger - Both fans on high

 

there has to be a better way to do that.

 

Pre-05 trucks only have 2 triggers to work with (a/c +12V and PCM ground for temp). The only way I can think of would be to do some kind of either time delay or slow-ramping relays, or to go to a standalone variable speed controller.

 

the stand alone may be the only way. All I know is there is a horrible "shock" on the charging system with this set up....one I am not willing to live with.

 

The 05 fans can draw up to 75 amps of power. I have put a DC shunt and from one fan on low and kicking the A/C on then both fans on high it drew 75 amps. The Nelson harness is fully capable of supporting this(not for a constant high amperage). After the initial start up the amperage levels off to around 7-8 amps both on high.

I have the Nelson harness with the 05 Fans. I know this may sound odd but you may have too much amperage in your system for the relays. I have the stock 105a alt and can only make a small amount of amperage, where as you have a high capacity to put out amperage, hence you can put the full power to the fans to turn them on where i cant possibly over amp the relays, you can. this may be the problem. Not sure tho.

Does this make sense?

 

Ummm, No! LOL

 

I run a 105 too and still feel the system shock

 

If the fans are pulling 75 amps when the activate then ANY alt is going to have a VERY short life.

 

I have the LS1 fans with the Nelson Wiring Harness and I have my Fans come on at 180 because I have a supercharger and the truck still runs at 14 AMPS with Factory Batttery and Alt. My truck still creeps up too 190 when it is 100 outside which means my fans run constantly and it still stays at 14 AMPS.

 

I think you are confusing volts and amps. The only way to find out how much current (amps) the fans are drawing when they are running is to put an ammeter (shunt) inline with them. The systems will always charge at 14 volts (what you are referring to) unless you exceed the capacity of the alternator. The reason people are seeing system shock (voltage drop) with the fans is because the alt may be sitting there comfortably producing 60 amps of current, then BAM the fans turn on and all of a sudden there is 135 amps being drawn off the alternator and it can't adjust that quickly. As the alt output increases and the initial startup load of the fans drops off, the voltage comes back up to 14 where it should be.