Electric fan load causing too much of a voltage drop

[anguilla1980]

I have an electrical issue that for the past few months I have just lived with, mostly because my car was apart doing the suspension. But now it's time to attack it.


I have this alternator in the 180amp idle 1 wire version: https://www.qualitypowerauto.com/catalog.php?item=551

I have this fan setup from C&R/SPAL: https://www.crracing.com/product/che...r-module-sb-bb

I'm running 2 30amp fan relay kits w/fuses from Summit, I think the Perma-Cool kit.

I have this electronic programmable duan fan controller: https://www.summitracing.com/parts/dak-pac-2750

I'm running TEMco 4/0 welding wire for the alternator (w/500F heat shielding) and grounds. New Odyssey battery.

My ground goes from my battery to the alternator bracket at the engine block, from the engine block to the front frame/radiator support, then from the rear of the body back to the battery (battery is in the trunk). All using 4/0 welding cable. On the way back from the battery, my positive wire goes to a giant 4 post 3/8" block on the firewall. Power goes straight from there to the fan relays via 8 gauge wire. The fan relays are grounded to the radiator support using sheet metal screws and as mentioned, the ground from the engine block is indeed grounded at the radiator support where it meets the front frame.



Everything on my car works fantastic, but when these fans kick-on, the voltage on my DD gauge goes from just below 15 all the way down to 13, sometimes even 12.8/9 at a stoplight. Just 1 fan isn't that much of a problem, but when they are both on when the car is hot or with the Vintage A/C, the harness voltage just drops. I was thinking maybe the alternator wire was getting hot and adding resistance going along the valve cover/intake even in it's heat sheilding, but the fact of the matter is that it happens when on a cold start if I switch the A/C on to turn on both fans.

Any idea where to start? Everything is new and I thought sized appropriately.

Thanks!