I currently run LS1 fans and I have the stock 105 amp alt. With the headlights and radio on, there's a serious voltage drop down to like 13 amps when the A/C compressor kicks on (and both fans come on high). Will the 145 amp factory alt stop this? Did GM ever put a 160 amp alt on the trucks? These should be bolt in to my current setup right? Thanks

 

145 will do the trick. Mine has stock efans and 145 alternator. It would dip occasionally. Bar none the best upgrades were 0/0 wire from the battery to the back of the alternator and 0/0 from the battery to the power distribution center. Ditch the lead acid battery and go with a gel cell.

 

I have a 145 amp alt with ls1 fans and I have not noticed any significant voltage drops. I usually can't even tell when the A/C or fans kick on. Although I would say I didn't really have too much of a problem with my 105 amp alt until it died on me so I wouldn't guarantee a 145 amp will solve your problem.

One thing I will tell you is DO NOT by a rebuilt alt from Autozone and I doubt any of the other autoparts stores are much better except maybe Napa. I got a reman from Autozone because they had it in stock when I needed it. Within 6 months I have already traded it for another and it's not any better. It looses voltage above 4500 rpm, I suspect it's because the springs they use to rebuild them are cheap and too weak to keep it charging at high rpm. Stupid thing has plagued me something terrible and I think it is the cause of a TPS code causing REP at long WOT runs.

I'm getting an OEM take-off alt when I get home from my Christmas trip and pray that solves some of my problems.

Also yes the 145 amp alt is a direct bolt on and you will need a slightly longer belt with it.

 

I would never use an autozone alt. I am very weary of anything not OEM and try and use GM parts when at all possible.

Truckmann, are you using a two pin or 1 pin harness?

The OEM harness is a two pin style, but the kind I am using is 1 pin so whenever the A/C compressor comes on (comes on even if you are running heat in the winter to dry out the air) the fans kick on high. The two pin high speed fans come on when the A/C compressor reaches a certain pressure. I think this would reduce the number of times the fan kick on high and be easier on the alt.

As it is right now, I need to get a bigger alt in. As it is right now, my stock alt will be dead in short order. I'm actually considering just cutting the A/C trigger wire. I don't need high speed fans in the winter anyways.

 

Are you able to rewire your harness to use the A/C pressure control and not the compressor trigger on your year model? I did this on mine and it made the fan turn on much better. Voltage drop might still be there but I don't notice it in traffic or stoplights anymore. Much better. I have an 04 with the 05+ efans with stock alternator.

If I remember correctly, you have EFILive too so that makes things even easier...

 

I should also add that I had the A/C compressor trigger type harness with my LS1 fans and I always hated sitting in traffic or idling. I reworked the nelson harness to use the two pins.

 

Yeah, I could do that. Supposedly there's a way to redo the 1 pin harness with another relay to do 2 pin, or I could just buy a new two pin harness. The new harness would be 90 and I could probably sell my current harness for $50. So $40. Although the root of the issue is the alternator so it may be wise just to get a new alt.

 

Yea, you could add another relay that uses the ground the pcm creates as a trigger to supply 12V to the A/C trigger wire.

It's also pretty easy to rework the harness with the current 3 relays. KySilverado's thread has all of the popular harness diagrams IIRC. If you are good with circuit diagrams or want to learn, I suggest doing this. You don't have to change much.

New alternator couldn't hurt either. Reliability always come before performance in my book.

 

I had my ls1 fans on the truck with stock 105 amp for about four months, with occasional drop to almost 13 volts. Just put my new remanufactured 145 amp alternator on monday and havent noticed any drop.

I'm using the hayden fan harness which i have wired up to kick both fans on at the same time on high. MY stock 105 was doing fine, but i didnt trust it much longer bc its already 7 years old.....

 

My '06 Tahoe came from the factory with a 160-amp alternator (KW1 code in the glovebox). Not sure if it was part of any equipment package (Z71, trailering, etc.), but I don't have any voltage issues.