Burnt wire... how did this happen?

[GregWeld]

You say FANS -- as in plural -- which says you should have RELAYS - as in PLURAL -- One relay PER FAN... and a separate power lead to each relay.

To keep that "neat" -- you'd use a distribution block. SO a wire that is capable of carrying 60 amps - to a distribution block - then power wires capable of 30 amps - one to each relay.

The ignition switch wiring carries very little amperage so can be "light" gauge -- and the one wire from the ignition can be used to switch both Relays -- ditto the "trigger wire" (from the temp switch)...

Ground both relays right near where they're mounted. If the surface is painted use a star washer between the paint/primer and the lug. I always use a flat washer between the lug and the fastener.... that way as you tighten it up - the fastener can spin against the washer rather than twisting your lug/wire. It's best to clean off the paint clear down to bare steel... but sometimes that just makes a problem. So the star washer is made to CUT into the paint and get to metal. Remember - the GROUND is just as important as the power side.