Heat exchanger fan wiring

Tim Moland

Well-Known Member
Wiring is definitely not my strong suite. I'm trying to wire up a heat exchanger fan for key on operation. Lonny has laid out where to tap into the bcm plug to get power. It is 2 wires that get wired into one. But one of the wires in the terminal in my BCM plug appears to be used on something already. The second one is cut. The harness was assembled by DF, so I don't know what it goes to.
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I'm running a heat exchanger in the engine compartment, so I will be running it to the back of the car. Is there a different terminal I can tap into that will be powerful enough for the fan?
 

JPas914

Well-Known Member
You could build a relay, and use the ABS circuit/fuse as the trigger to activate it since it is still being powered when the key is turned on. My heat exchanger pump and fan were a slight after thought when I had built my Goblin.
 

Rttoys

Goblin Guru
Yes. That can be a trigger for a relay. You can use a “Bosch” relay or a 4 prong. I need to find my little tutorial I made years ago, but basically you have 12v power in (from batt). 12v power out to fan (when triggered). One ground and one ignition positive to trigger the relay. Don’t be afraid of them, they make life simple.
 

Tim Moland

Well-Known Member
Ok, I'm thoroughly confused. Like I said, wiring is not my strong suit. Why would I do all this relay stuff as opposed to just wiring direct to the BCM plug? I don't understand wiring
 

JPas914

Well-Known Member
It's all just like the saying 'there's more than one way to skin a cat'.

The relay will power the fan and pump when activated by the trigger, which would keep the amperage draw on that wire down. You can easily buy a small 'add-a-fuse' plug at Autozone to tie into the ABS fuse. it help keep all the wiring in the back without needing to run it through the tunnel, or worrying about where that one wire goes to. Building the relay is a very simple process.
 

Rttoys

Goblin Guru
If it was a low amperage item being added (like led lights), just adding the wire would be fine, because the bcm can handle it. Adding a higher amperage item like a fan, it’s best to add a relay so it handles the load and the bcm is nothing but a trigger. I did the same thing to mine because I added a larger inter cooler fan than DF provided.
 
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