The Cart Before the Horse: Spec 3 Build

[Jake]

Mine has power being pulled off the battery wiring under-hood (where you'd hook up to jump it) and ground from... wherever. I am using a relay so the switch isn't hard wired to the fan itself.

From my M3 thread (this is why I wrote it all down):

or my own later reference...

Relay:
30: +12V from car
85: Ground
86: To in-car switch
87: Positive wire from fan
87a: Ignore

I grounded the relay and the fan both to a common point that is used near the battery jump point, and ran the +12V for the relay and fan off of the battery jump point "distribution box" thing.

The relay itself is an Amazon special and is something like this (although mine may be considered waterproof, I dunno):

https://www.amazon.com/Pack-EPAuto-Relay...G7SHRFPRA5