Installing Electric Fan

Wiring up an electric fan and on the relay, not sure if the ground wire should go to 85 or 86. Any help would be appreciated. Thanks

Dobaroy said:

Wiring up an electric fan and on the relay, not sure if the ground wire should go to 85 or 86. Any help would be appreciated. Thanks

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I'm sorry, i'm prett decent with wiring up things like fans but i'm gonna need waaaay more detail. Aftermarket? Junk yard? 85 or 86 - maybe its just me, but not sure what you mean there.

He's talking about the 85 or 86 pin on the relay. I have NO clue as I'm really stupid when electrical has more than 2 wires, wish I could help.

#30 terminal= Constant 12 volts (+ side of battery)
#85 terminal= Ground
#86 terminal= Manual or thermostatic switch
#87 terminal= Switched 12 volts (with key)

Thanks for the replies. We are working on an new electric fan that runs with a 40 amp fuse and we installed a 20 amp stat with it. Supposedly if we used the relay the stat would not fail. This is how we have it hooked up right now:
#30 with 40 amp fuse from 12 volt (#10 Wire)
#87 to Fan (#14 Wire)
#85 to Stat (#14 Wire)
#86 to Ground (#10 Wire)
However the stat failed so thought now we would just go to a switch, the reason for my question was that I thought we wired it wrong. THinking now maybe the 20 amp Stat won't work with 40 amp Fuse although the company we bought the fan from says it should.
Thanks for all your replies.

67 B-body, the fan we are working on runs on a 40 amp fuse and we have now tracked down a 25 amp stat with a harness on it for a 40/60 amp relay. We are thinking of getting the 40 amp relay because I don't think the relay should be higher than the fuse for the fan. If you think this will work, would you let me know. Thanks

Dobaroy said:

67 B-body, the fan we are working on runs on a 40 amp fuse and we have now tracked down a 25 amp stat with a harness on it for a 40/60 amp relay. We are thinking of getting the 40 amp relay because I don't think the relay should be higher than the fuse for the fan. If you think this will work, would you let me know. Thanks

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The control side of the relay should pull very little Amperage! The thermostat should be on the control side (where I show a switch in the drawing). You'll notice that I fused the switch power (this controls the relay) at 1 Amp. A 25 Amp stat is 25 times higher than my little 1 Amp fuse and toggle switch. I'm not sure why your stat would fail at such low current draw? If it were me, I would use a meter set to amps, and see how much draw your relay takes to pull in the internal contacts. If it's anything more than an amp I would toss it out. This should be tested with a temporary jumper wire from +12V to the T85 terminal with a meter set on AMPS in between. Make sure you have good -12V (ground) on terminal T86 as well!
Remember that when sizing your conductors for this circuit, you must consider the amp draw of the control circuit (relay itself) provide a conductor (wire) that meets this requirement, and make sure your switching device can handle this load (your thermostat).
Also look at the current draw of the device your powering. The relay has to have this capacity on the load side of its circuit plus say 10 to 15%. Now you have to choose the correct conductor (wire) to handle that load with the 10 to 15% added. Your fuse should be rated at this point to protect the device, unless the device has its own built in load protection. If it does have a built in current limiting device, you should fuse the circuit according to the conductor (wire) capabilities / size.......
Hope this helps!

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BTW,,, 40 AMPS seems high for an electric fan!!!! I think the cables (harness) might have the 40 AMP rating, not the motor it's providing power to.....
If it is 40 AMPS, I hope you have one hell of an alternator....

Thanks for the reply 67 B, quite a bit of info to get my head around. Yes, I think you are right, we need the meter to tell us how many amps are being drawn. The alternator that is on this car now seems to have stood up to the fan for the short while that we ran it. It is a 120 amp one wire GM alternator. So I hope that part of it will stay together. Will let you know how we make out.

Dobaroy said:

Thanks for the reply 67 B, quite a bit of info to get my head around. Yes, I think you are right, we need the meter to tell us how many amps are being drawn. The alternator that is on this car now seems to have stood up to the fan for the short while that we ran it. It is a 120 amp one wire GM alternator. So I hope that part of it will stay together. Will let you know how we make out.

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Glad to help....