Adding external relay

[tim richey]

Cooling fan not working due to melted pin so I’m adding an external relay. I got power to #30 and green yellow wire from resistor to #87. Where am I getting signal for # 86 and ground for #85?


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[07 Boss]

85 you can ground anywhere, 86 is your signal wire to turn the relay on.

 

[tim richey]

So 86 needs signal from the temp switch so it comes on when it gets hot?


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[MrBhp]

I pulled mine from the original wire inside the box.

 

[Laga]

Make sure your ground location is clean. Sand it down if necessary.

 

[07 Boss]

So 86 needs signal from the temp switch so it comes on when it gets hot?


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Depends. What part of the system are you bypassing? Where is the burnt pin? If it's after the ecu you can just take the signal wire from there that went to the fan. If the burnt pin is at the ecu then you need to find another source. I have an external relay hooked up but use a manual switch to turn on the fans and pump when the motor is off and they run normally when the motor is running.

There is no temp switch to turn on the fans. You have a cylinder temp sensor that outputs an analog signal then the computer determines when they go on. You can't just run the signal wire from the cylinder head without another switch. You would have to determine the voltage for which you what the fans to come on and set the switch accordingly.

Again what part of the system are you bypassing?

 

[MrBhp]

The burnt pins are in the fuse box usually. When you separate the upper from the lower you get access to the burnt wire. I just cut the wire before it feeds into the old slot and run new wire to the new relay. IIRC. Which I might not.

 

[tim richey]

Burnt pin for low speed fan


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[tim richey]

This is the relay I have to put in


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[07 Boss]

Burnt pin for low speed fan


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You need to take the wire that goes to that pin and run it to the relay. When you trigger 86 it connects 30 and 87 to complete the circuit.

 

[tim richey]

You need to take the wire that goes to that pin and run it to the relay. When you trigger 86 it connects 30 and 87 to complete the circuit.

I’ve got that wire ran to #87 on the external relay


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[tim richey]

You need to take the wire that goes to that pin and run it to the relay. When you trigger 86 it connects 30 and 87 to complete the circuit.

I guess I’m just not understanding what wire goes to 86


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[DieHarder]

YouTube explanation of the circuit:

 

[tim richey]

YouTube explanation of the circuit:

Yes I have watched that video a couple times. Still doesn’t help find a trigger wire for low/hi speed fan from the ECU


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[brasil]

..the trigger wire should be the wire that appears in the fuse box... . The trigger wires are the ones with BLUE Marks. in the video they are located on the left side...

 

[MrBhp]

Pictures of one that I reworked. Unfortunately I don't have any pictures of the box taken apart. I recall having to trace the wire down from inside the box because my electrical skills suck. Probably not a big help to you.

 

[brasil]

Besides the electric fan... I would like to have a "real fan ". Like back in the old days. My 1990 Fox Body had a true riged fan. Bolted on the waterpump...
I am thinking about doing a "swap" . Perhaps someone here already had the same idea ?

A fan clutch ( thermal ) a fan... and a shroud. that´s it.

 

[MrBhp]

Besides the electric fan... I would like to have a "real fan ". Like back in the old days. My 1990 Fox Body had a true riged fan. Bolted on the waterpump...
I am thinking about doing a "swap" . Perhaps someone here already had the same idea ?

A fan clutch ( thermal ) a fan... and a shroud. that´s it.

That seems like a power robbing step in the wrong direction. I think there are still the usual four bolts holding the water pump pulley on. You would need to fab up some kind of cowl for it of course. Get the spacing right for the fan, etc.

 

[07 Boss]

Besides the electric fan... I would like to have a "real fan ". Like back in the old days. My 1990 Fox Body had a true riged fan. Bolted on the waterpump...
I am thinking about doing a "swap" . Perhaps someone here already had the same idea ?

A fan clutch ( thermal ) a fan... and a shroud. that´s it.

Yeah, I guess you could but why??? Taking a step backwards as far as efficiency of the cooling system and adding more parasitic loss to the motor. Why do you think it's better?

 

[07 Boss]

I’ve got that wire ran to #87 on the external relay


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OK, think about it this way. The pin is burnt so you need to complete the circuit. You need to put the relay in the same spot as the burnt pin (not physically) in the circuit. The way the relay works is that when you give power to #86 and it connects #30 and #87 So you need power to #30 and #87 goes TO the fan not from the fuse box. The wire that goes to the burnt pin must go to #86, and #85 should be a ground. So when your ecu tells the fan to come on it will send power to the burnt pin and it does not come on. So now you take that signal, before the pin and run it #86. This way when the ecu sends a signal to the fan it closes the relay instead. When the relay closes it send power from #30 through #87 to the fan.