PCM cooling fans

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Oct 8, 2023 | 10:52 AM

#21

LSswap

TECH Fanatic

Joined: Nov 2014

Posts: 1,309

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Quote:

Originally Posted by kglowacky

makes sense. to clarify use a small gauge wire and ground where?????. It seems all grounds end up in the same battery system on the truck.

You can use a small for all the relay grounds to the same place the PCM is grounded to the chassis. A big wire for the fan to any other chassis location. They all end up at the same place, but there are losses and noise generated in ground wires and you want to keep that away from the ECM. I may be over engineering this, but I like to keep my power and signal circuits separate.

Oct 8, 2023 | 04:04 PM

#22

kglowacky

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Joined: Sep 2023

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Quote:

Originally Posted by LSswap

Here's what I am thinking. Leave my current temp (PCM) wiring as is. Rewire my a/c relays to a neg signal output and tie the neg relay signal to the pcm wires before the relays on the temp wiring. This way no power ever gets to the system until after the Temp relay as it works great currently. Basically doing what you show using 87 and 30 as my run thru on a/c relay (neg signal) to pcm feed. . Only concern I have ,only because wiring is not my strong suite is do I need diodes or will neg feed into a neg pcm feed cause a back flow that is going to burn up the pcm. You show one diagram with diods one without.
Hope this makes sense. Basicly from my diagram I will reverse my relays on the a/c side only and connect the neg feed from the relays to the 2 pcm wires coming from the pcm.
I hope this makes sense

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