My 70 Nova project (Formerly looking at this mustang)

Thank you...
 
You are very welcome. Glad I could help.
 
Working on wiring my my radiator cooling fan and although I've done them many tiems before this is different. Usually you provide a ground, a fused hot wire, and the turn on wire controlled by something or other.

With the computer controlling the fan it provides a ground to the fan. Somehow I don't think the computer can handle a 30 amp 3000 CFM fan without a relay.

So I bought a heavy duly waterproof relay I'll mount right under the fan so I can kind of hide it but still be accessible.

I've never been an electronics wiz and I freely admit that. So my plan is to run a ground wire to the fan motor. Then run a fused hot wire to the relay for both the power and the turn on pole. It will be fused hot all the time. Then run a wire to the relay ground terminal and have the computer ground out the relay to turn the fan on. That way the computer doesn't see the heavy switching load of grounding the fan out as the fan is grounded separately.

I realize that relays as far as I know aren't made to be hooked up this way, but will it work?

I've attached pic of the relay. I "think" I need to run pin 86 and 30 to fused power, then run #85 to the computer ground. 87 and 87A won't be used.

So am I all wet on this? Won't be the first time if I am.


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I'm far from an electrical wizard and look forward to our expert's inputs, but I should think the computer's ground output to trigger the fan is sufficient to trigger the relay. Simply use the relay to switch in a heavy ground wire. Something like this: 85 is 12V+, 86 is 12V- from the computer, 30 is your heavy-duty ground and 87 is your heavy-duty ground going to the fan. The fan will have a fused 12V+from the battery (always hot in case the computer keeps the fan on after the ignition is turned off). What do you think?
 
I hadn't thought about wiring the fan fused hot and using the relay to turn on a ground for it.

So run ground to #85, hot to #86 and the fan, and ground to the fan from #85?
 
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Run a battery 12V+, fused wire to 85. Connect the computer's fan output ground to 86. When the computer sends the ground signal, the coil in the relay is energized and it flips the switch (30, 87, 87a). When the relay is not energized, in your case, when the computer is not sending a ground output, pins 30 and 87 are connected. You won't put anything on 87. When the computer sends the ground signal, the coil will energize, and 30 will switch from 87 to 87a. 30 will be the heavy-duty ground, and 87a will be the heavy-duty ground to your fan.

I can't think of the term used to describe it, but pins 85 and 86 don't care which one is positive and which one is negative as long as one is + and the other =. I hope I'm not making this more confusing than it is.
 
I hope this makes more sense
85 - Battery 12V+
86 - Computer's Fan Output
30 - Chassis Ground
87a - Fan Ground wire
87 - Not Used
 
The computer supplies a ground, will this work to #86? I thought 86 was a switch on wire requiring 12v?
 
alloy said:
The computer supplies a ground, will this work to #86? I thought 86 was a switch on wire requiring 12v?
Click to expand...

So, in other words, your question is, will the computer successfully provide the fan ground (and not throw a code) when it is grounding a relay coil rather than grounding an actual fan motor.

Is that what you're concerned about?

I don't know the answer to that question. Hopefully Gaffer (or other) can answer it.
 
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