Hi Gsab,
I am having the same problem when the 2 x Davies Craig Fans I purchased come on, they voltage drop the car heavily the alternator cannot keep up. I am attemping to wire in a PWM setup but scratching my head at the configuration required to set it up. I have it wired in using the haltech diagram, can you provide some insight?
Attached is the Haltech diagram I used, I am using the 100A SSR from Jaycar, and the diode suggested in the diagram, the resistor i felt was redundant as the Link Fury has its resistance built in.
Can also confirm that the wiring works as when i run the AUX output as Test PWM, the fans work fine.