Put the Sierra in the garage and went to work on the e-fans.
Didn't take me long to track down what happened (and I have to give credit to another Amazon customer who reviewed what I bought)...
One of the three relay connectors melted. Here's a pic from the reviewer (this isn't my harness or 'me')
View attachment 104829
With this harness, the leads from the +12v source to the relays (both fused with 40A) and the leads from relays to fans.... are two different gauges.
Working backward, the fan <> relay wires are 8ga.
But the relay <> +12v power wires... are 12ga.
Too much resistance in the small gauge wire... creates heat... and melts the relay connectors.
With mine, only one of the three was melted, but it looked very similar to the one on the RH side as shown here.
As I mentioned in the other post, the two 40A fuses were intact. These run from remote power lead (the red 'battery' box near the alternator, that the alternator connects to, where it's advised to connect to), and the relay plug connector.
I also noticed the corresponding +12v pin on the relay was burned.
So, now, I have a couple of choices...
- Reverse engineer the harness, put in new relays / connectors, and beefier wiring in at least the 12ga connections (I'm sure I could do it, although I'd have a ton of splices... )
- Build my own harness from scratch (basically salvaging only the two plugs that connect to the fan motors)... which I could probably also do, but would take me a longer time (cause I'd want to do a 'pro' style job with it)
- Buy the correctly engineered harness from someone like Nelson Performance, and pay 3x the amount. Spendy, yes... but look at the bullet I dodged here, both from an electrical and an engine standpoint. I'd rather not repeat what happened, again.
And for those asking, the GM harness (for the '05-'07s, which had this as OEM), connect a bit differently... they have a subharness that branches from the main wiring harness, and a subpanel off the main battery box. So that's really not an option, given my '03 (unless I'd go find an '05-'07 harness / battery box and plumb it in... which would be crazy to do).
Since I have some other stuff going on which requires attention, I'm thinking my best / safest bet is to spend the coin and order the better quality one from Nelson Performance.
For those wondering about the item on Amazon which I now recommend you stay away from, it's:
I'll also link to this post from my writeup, when I installed this several months back, as a warning about this part.
TL : DR; "You get what you pay for"