YenkoST

iTrader: (11)

When the electric fans come on with the A/C on, its an instant on/off and the truck likes to surge a little bit when that happens. Its not like a compressor surge but an electrical surge from a big drop of voltage all of a sudden. Which probably hurts mpg a little bit and definately hurts performance with the A/C on. Any way around this?

thunder550

iTrader: (70)

I looked into this for a long time. I ended up running a DCcontrol electric fan controller because it is variable speed and semi soft-start. In the end I ditched the e-fans and went back to the clutch fan because I couldn't get the truck to stop overheating while towing. I did like the DCControl deal though when I had it. Nice controller.

YenkoST

iTrader: (11)

Yea, I don't tow with it except maybe once in a while but just looking at it in a mpg sense. Might have to look into the DC controller. Right now the computer does it all.

4ws f 7

I have read you need the 145 amp alternator to fix this issue. Also IMO this mod should be done with only the factory 34 inch radiator, and the factory E fans.

budhayes3

iTrader: (19)

I have 05 efans, 34" radiator, etc, and a 145 amp alternator and my truck surges fiercely when the a/c compressor kicks on and the fans come on high.

4ws f 7

At this point I have a Nelson harness, but will be switching over to a factory harness in the next few weeks. Which harnesses are you guys using? Also I think I read something about the correct alternator having surge dampening? Not sure on this but thought I had read this somewhere. I am not a engineer and will be copying G.M.'s hook up exactly the way 05 up 1/2 tons are. I have read a lot about this E fan mod and a lot of people have had issues. I hope by copying G.M. exactly I will end up happy, as I believe this is a worthwhile mod. Mostly for A/C cooling at idle which was poor in traffic, but I don't like the fact that Nelson's harness has the fans come on the second the A/C compressor is engaged, G.M. has it done by A/C pressure which to me makes more sense, IMO. I never would have thought this E fan mod would be this much hassle, and I have to admit this is one of those cases where the more you know, you realize the less you know. Good luck.

YenkoST

iTrader: (11)

I was thinking the BIG 3 might help with this a little bit.

Eye-P

iTrader: (2)

I just switched the Nelson harness A/C trigger wire to the #2 fan PCM pin.(33?)
This is how GM does it- I think. Not much of a surge problem any longer.

budhayes3

iTrader: (19)

Yea I have the Nelson harness too...I totally agree that if it can be wired and tuned the factory way there wouldn't be a surging issue. I don't think that my 02 PCM is capable of the tuning though. If it is and tuning + a factory harness is the cure, then I'd be all over that as fast as I could get the cash up. As it is now I plan to wire in a 4th relay to switch the a/c signal to the nelson relay on and off, so I can keep the high fan off when it's sub 30* out and I have the defoster on and I'm sitting for 10 minutes waiting for a freight train to pass

Eye-P

iTrader: (2)

I seem to remember Justin posting that the 02 PCM can in fact use the second pin out for fan control. I would PM him and ask.

That AC trigger drove me crazy.