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Dual Fan Wiring

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Old Jun 16, 2020 | 09:01 PM
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Dual Fan Wiring

I have a 1988 iroc with some dual fan wiring that I am trying to repair. I found the dual fan connector I think I need as well as the pigtail for the existing wires on the car. My question is that on all the new harnesses there are only 5 wires while there is 6 different (2 orange, 2 light brown with a white stripe, 1 grey and 1 green with a white stripe) wires coming from my car. Does anyone have a picture at how there's is wired? Any help is appreciated.


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Old Jul 23, 2020 | 09:21 PM
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From: pawtucket RI
Car: 1986 iroc
Engine: alum. head 350 supercharged
Transmission: 6speed
Axle/Gears: ford 9in 3.90 35 spline moser axles
Re: Dual Fan Wiring

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Old Jul 23, 2020 | 09:21 PM
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From: pawtucket RI
Car: 1986 iroc
Engine: alum. head 350 supercharged
Transmission: 6speed
Axle/Gears: ford 9in 3.90 35 spline moser axles
Re: Dual Fan Wiring

this should help you
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Old Jul 23, 2020 | 09:23 PM
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From: pawtucket RI
Car: 1986 iroc
Engine: alum. head 350 supercharged
Transmission: 6speed
Axle/Gears: ford 9in 3.90 35 spline moser axles
Re: Dual Fan Wiring

in that picture you need to locate the other relay as there is 1 per fan
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Old Aug 8, 2024 | 12:38 PM
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Re: Dual Fan Wiring

Is it possible to run a jumper from the green/white wire from the main fan over to the other relay to make both fans run at the same time when the ecm sends the signal?
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Old Aug 8, 2024 | 01:08 PM
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Re: Dual Fan Wiring

Yes. The green/white wire is simply the ground trigger from the ECM to activate the relay. Very low current demand on the ECM.

You should be able to T off that wire and run it to both relays.

The only thing is for safety you'll want to maintain the A/C pressure switch too, so you'd tie that wire that into the green/white wire as well. But in your case now, both fans will come on when that switch gets grounded, rather than just the secondary fan.


Last edited by ULTM8Z; Aug 8, 2024 at 01:13 PM.
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Old Aug 8, 2024 | 01:23 PM
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Re: Dual Fan Wiring

Funny thing is.. (and i will check tonight after work) i think both relays have the green and white wire.. My ac doesnt currently work (I have new compressor and all that just havent installed) Are you saying that so the fan will kick on when ac is turned on?
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Old Aug 8, 2024 | 03:41 PM
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Re: Dual Fan Wiring

Originally Posted by fleming3310x
Funny thing is.. (and i will check tonight after work) i think both relays have the green and white wire.. My ac doesnt currently work (I have new compressor and all that just havent installed) Are you saying that so the fan will kick on when ac is turned on?
Then maybe a previous owner did something custom? According to the schematic, the other one should have a grey wire. Which I think was more to notify the ECM that the secondary fan was on, since the secondary fan is activated by a coolant switch.

Unless the ECM would activate the fan via the grey wire if it detected the A/C on. But that would have required the ECM to see AC compressor activity and I'm not that sure about pre-1990 ECM's.

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Old Aug 8, 2024 | 08:43 PM
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Re: Dual Fan Wiring

So it did have another green and white wire.. I ran a jumper from the other relay over to relay #2 and now both fans kick on when it receives signal from ecm.. my only question.. when I get ac going will it hurt anything if it sends a signal thru the air conditioning to that relay? I think that green wire makes a ground .. not sure about that.. I don’t want to burn anything up.. I’m glad this worked as I was about to buy a new aluminum radiator and fan set up.. it doesn’t creep in temp any longer..


someone def did some wiring work as I found a spliced section with electrical tape on it.. I will solder that this winter and neaten it up with some new loom.. it’s kind of hid I didn’t know it was like that .. thanks for your help!
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Old Aug 9, 2024 | 08:26 PM
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Re: Dual Fan Wiring

So.. do these cars have 2 of the big relays ( one for each fan) or just one that works both? My car has 2.. I was looking at replacement. Harness and it has the main harness plug.. a plug for each fan.. but only one relay plug..

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Old Jun 14, 2025 | 06:56 PM
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Re: Dual Fan Wiring

Originally Posted by ULTM8Z
Yes. The green/white wire is simply the ground trigger from the ECM to activate the relay. Very low current demand on the ECM.

You should be able to T off that wire and run it to both relays.

The only thing is for safety you'll want to maintain the A/C pressure switch too, so you'd tie that wire that into the green/white wire as well. But in your case now, both fans will come on when that switch gets grounded, rather than just the secondary fan.
Are you saying t tap the green/white wire from primary fan and tap it into the secondary fan relay green/white wire?
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Old Jun 15, 2025 | 10:06 AM
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Re: Dual Fan Wiring

Correct that’s what he’s saying
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