The harness I designed operates the same as the nelson harness. I am using a 2 fan LT1 set up.

1 fan high when AC is on but temp is not high enough.
1 fan on high when AC is off but temp is high enough
2 fans low when AC on and temp is high enough.

Never are both fans high at the same time. At most 1 of the two i is on high or both are on low.

That is the stock operating levels for those fans so I dont think it will affect the Alternator in any negative way....

 

either fan 2 on high or fans 1 and 2 on low..
My fans come on low with the AC on, or when it gets up to 205*.
If my coolant gets up to 215 both my fans will come on high..
My fan #2 never goes high by itself unless i turn it on with a switch inside the cab..

 

And those are the things that I am trying to get around. On a 05 both fans come on high when the high side is high enough. On the 99-02 they dont but if you add the relay you can get them to operate on high with AC on and then they will shut off when you want them to ie high way speeds. Also the fans will act normal with AC off. I did not want to add a switch in the truck for high if you have a option to do with a relay and the PCM.

 

Do you need both fans on high?
Thats some serious amp draw and alot of airflow.

 

I would like to have both fans on high with the AC on. Watching the high side with fans on low and 115 outside they get pretty high. The way I see it is that these fans were designed to come on high with AC on a hot *** day. Might as well get all I can out of them.

 

I ran fans on low speed manually (2004 1500HD) for 40 min, temp never got above 196. Both fans running low speed moves plenty of air.

 

All you need to do is change your FAN#2 parameter settings.

I used the fan settings from '02 Camaro. Works great.

 

Yeah why dont you just change your high fan (setting 2) to come on at whatever temp it tries to drive it up to with ac on? Like 200-205 degrees?

 

since the last post in this was on 07-26-2012, 08:24 PM i hope he figured it out lol