Electric Fan pin 33 and 42

[bh2fan]

Hello,
Trying to do an electric fan conversion on an 05. I have read that there are two output pins (pin 33 and 42) that can be enabled to control two electric fans.
From what I have read, most people use pin 42 only, why? Can anyone explain the functions of pin 33 and 42? Does only one pin turn on the fan when A/C is on? Does the PCM turn off the fans when a certain vehicle speed is reached?
I know that 94-96 B-body vehicles have two pins and fan 1 turns on when temperature is 225F and or A/C head pressure is above 189psi. Fan 2 turns on when temperature is 232F and A/C 240psi. Both fans do not come on when vehicle speed is above 45 mph or so. Is it something similar for the H2? Thank you.

[bh2fan]

For anyone else who is interested the answer can be found here:

http://www.silveradoss.com/forums/index.php?showtopic=45645&st=0&gopid=531884&#entry 531884

In summary, pin 42 is used to turn on fans on low speed and 33 on high. Works similar to the B-body setup except fans have two speeds.

[tomp]

Nelson performance has the wiring harness you'll need. You will then want a programmer that supports electric fan on/off temp controls such as the Diablo Predator. Finally, you will need to send them your OEM map (using programmer and serial cable) so they can enable power to those pins using a custom built map that MikeL can send you from their forum.

[HUMMERcustoms.com/TAZ]

Had discussion with Hummer on this and was decided that in my case since I was looking at maximum cooling at all times due to the boosts etc. etc. that I use pin 42 only as I want SC aftercooler as cool as I can because the max temp it may be at without problems 240F is pulled through many of those other cores. I will not go on any more as any here who have run SC high boost plus all the sprays understand max cooling at all time so if called for better it be there than have extra cooling come in late.

Now this is just for guy like me that is just messing around trying to billed an H2 dragster for track runs while I cooperate with Dragon to build a show rig and hopefully for SEMA this year or next. Have sponsors but, by time they are getting on board leaves to short of time so we are talking with them on next spring SEMA 2009 and then fall 2009. Whatever I want fast just to see what you can do with something that heavy but, still keep it street legal. So I run for coolest all the time and fans are set to come on at lowest temp they can.

If you had laptop tuning you can really do allot with fans using 2 pins. If you do not hae that and you live in hot area slow traffic maybe just run 42 pin so best cooling is there if needed and do not have to worry about all the setting and getting a handheld setup to allow you to do some fine tuning.

Whatever meets the need. Good Luck

TAZ