KySilverado

iTrader: (7)

Just installed the new GM fans on my 03 truck along with a new 34" radiator necessary to get them to fit. They look great and work well. I'm using the PCM to control them and hooked them up with the 3-relay wiring harness from Nelson Performance for the LS1. 2 Things

1> The 3 relay allows the single output from the PCM to turn on both fans on a low speed. If I understand the schematic correctly puts them in series and therfore getting only 6 volts each to make them low speed. Another wire is tied into the 12v lead and then turns on the passenger fan at full 12V and high speed to cool the AC condenser. When this fan comes on and it comes on a lot my voltage drops. Dimming headlights and interior lights. Very annoying Two things come to mind to fix this. One of the big capacitors I see out ther for the high power sound systems or a higher output alternator. What do you guys think?

2> For those of you thinking of using the LS1 Fan harness from Nelson for these fans there may be a problem. I'm going to call or write them to verify. Maybe they'll chime in here? The conectors to the fan motors fit but had to plug them in backward. I first plugged them in such that the clip clipped on but noticed that they did not fit well and when the fans came on they ran backward. (Pushed air out of engine bay). I just turned the connectors around. They fit as should and the fans run the right direction but just don't snap lock in. I'm wondering if this has messed up the circuits somehow? One other thing to mention is that when I was wiring them up I tested everything before plugging up the signal wire into the PCM it worked. I then kind of shuffled things around a bit and at some point tried them again and they did not work. There was a connector to one of the relays that did not plug into the base all the way and caused an intermitent function of the fans. I just had to seat it well. Just took a bit of trouble shooting to find it. Overall the wire harness is top notch and should last the life of the truck. Wish it had fuses in it. Didn't appear to?

04BlackSilverado

iTrader: (6)

The alternator should not be needed. The big capacitors you are thinking of are for a spike in power needs and will not work for the fans because of the constant demand for power. I think there is a wiring problem that is causing a short of some kind, not a dead short but close to it.
YOU NEED TO HAVE FUSES!!!!
I think that if you had fuses that they would have blown.
Double check all your wiring. Something is wrong.
Good luck

one03sierra

iTrader: (1)

the two gray wires that you hooked to the power cable are fusible links. there should be a slight draw in power when the a/c comes on due to that fan turning 100%. when the truck is up to temp both fans will come on at 100%. yes there will be a slight voltage drop anytime the fans are running.a capacitor will not help either. i am running the 130 amp alt. and at idle it will dim the light a little to.

raisinkane

A variable speed controller mentioned here sometimes...dcc?

..would that prevent this...

..would it come on slowly at first?

raisin

one03sierra

iTrader: (1)

no it is set up smilar. i used one of them also and it did not work as well as the nelson harness.

04BlackGmc

iTrader: (18)

Fans always draw lots of voltage. In my 94 bird when i turned the fans on my gauge would go from 14-15 to 9-10.

therock

iTrader: (2)

I have an 05 truck and there is no drop. It came OE with a 145 amp alt.
The needle twitches a tiny bit and at a stop sign at night in drive with the high beams on, foot on the brake, AC on, the lights just do show a slight dimming factor but only for a split second.

I think the factory relay system and at least a 145 alt is the way to go.

VortechC5

iTrader: (6)

Please let us know what the resolution of the problem is.

I am planning on the same setup using the Nelson 3 relay harness.

UPS destroyed the fans that I bought so I am waiting for replacements.

AKZ71

iTrader: (1)

I emailed Allen @ Nelson and he said that they are going to make an updated harness for the 05 fans. He is just waiting on his connectors from the supplier. They should be in sometime this week. He said that he will keep the site updated.

KySilverado

iTrader: (7)

I guess I am going to look into the higher amperage alternator. First comparing what is on my truck to what is in the 05. The 145 amp. Can anyone chime in what the 03 alternator is rated at? The voltage drops from 14 volts to about 13 when just the single fan for the A/C kicks on. Gonna try and lay my hands on an amp meter to see what kind of amperage they pull. I'll bet 20 amps easy. I have the Silverstar headlights and this drop is really noticable with them on. I have the automatic climate control system in my truck. I have found that in the auto mode, unless you manually turn off the A/C it cycles the A/C every 15 seconds thus turning this fan on and off with it. Frigging annoying. I've turned that off and its better.

Good to hear Nelson is going to revamp the wiring harness and have fuseable link. I think this is going to be a very popular mod. Guess I'll just figure out how to lock my connectors in. Would be a very bad thing for them to come unplugged