I wouldn't cut any holes in the shroud. Thats the reason for it. To create a vacuum and pull air through the whole radiator when the fans on and not moving. With holes you'd be pulling in air from the engine bay and not move it accross the radiator where it needs to go.

 

So, Nelson's harness cooperates w/ HPT? Can you get the fans to come on @ the temps you set?

 

Nelsons harness plugs up to the PCM in part anyway. With HPT you can set any temperature to turn this PCM output on or off.. Appears the newer 05 PCM have two outputs that you can control with HPT.

 

KY,

HPT has settings for temp - Stage One and Stage Two. Would this be one fan on, and then two fans on? Is there a way you could simply rely on the pcm only, or is the Nelson harness needed?

Thanks for your help.

 

Temp stage one and two are for later PCM's in trucks and F-Bodies. The PCM actually has two outputs Pin 42 and another?, and yes would control the fans 1 fan on 2nd fan on I believe. Would still need two relays for load carry. Settings for Fan Stage 2 does nothing in my 03 so i have to use the relays (nelson harness) to control fan speed and when they come on.

You don't have to have the nelson harness at all. You could fab your own. Basically you only have one on and off switch and you need the relays to carry the large amperage load and get creative on what fans to turn on and when. With one relay you could turn on both fans. 2 Relays turn on both fans but have lower rated relays by splitting the loads. 3 relays brings in the AC on the one and run the 2 at low speed like the nelson harness. Could get creative and put a timed relay in and power one fan and if it stayed on for a certian amount of time then turn on the second?

Hope all this ramble makes sense and I answered your queston

 

I guess I'm just simple. I used 1 relay for each fan and put a 2 toggles in the cab. One I have wired to turn on with ignition (when the toggle is on) and the other is totally on demand wether the truck is running or not. Never had a problem with overheating even when towing the travel trailer I used to have.