Input needed from someone familiar with wiring electric fans...

Katter281 · May 8, 2004

I'm wiring a MarkVIII fan in my 90 coupe and am having a problem.

I wired the fan using a 75A Bosch relay. With key-on, I can ground the thermostatic switch and the relay closes as it should. However, the fan won't turn on. I checked and have continuity between the battery and the end of the power wire for the fan. Finally, just to make sure the motor was good, I connected the battery to the plus terminal of the fan and it spun.

So, I'm getting power to the fan, the motor works, but it won't turn on. Anyone know what I might be doing wrong here?

89rdgt · May 8, 2004

I am taking it you have a 5 prong relay if no this will retain. You should have #'s on your relay or each prong 86&85 coil windings 87A, 87, and 30. You'll need 12v to 86 and thermo grounding switch to 85. When thermo switch grounds relay well engergize and close. Now youll also need a 12v source to prong 30 and then a wire from 87 to the postive on the fan. Than the negative on the fan to a ground. So in theroy thermo switch well ground the coil windings well engergize and 12v from 30 well flow through 87 and then to the fan. I hope this makes some sense. reply if you need some clearing up on anything.

Katter281 · May 8, 2004

89rdgt said:
I am taking it you have a 5 prong relay if no this will retain. You should have #'s on your relay or each prong 86&85 coil windings 87A, 87, and 30. You'll need 12v to 86 and thermo grounding switch to 85. When thermo switch grounds relay well engergize and close. Now youll also need a 12v source to prong 30 and then a wire from 87 to the postive on the fan. Than the negative on the fan to a ground. So in theroy thermo switch well ground the coil windings well engergize and 12v from 30 well flow through 87 and then to the fan. I hope this makes some sense. reply if you need some clearing up on anything.

I *think* that is how I have the relay wired as it stands. I got the fan to work a few weeks ago, but haven't changed anything. I guess I'll double check my wiring tomorrow morning to make sure I didn't fubar something.

Thanks for your input 89rdgt...

89rdgt · May 8, 2004

No problem always love to help a fellow stanger out. You may have already but just doulbe check all power and grounds too. Cant hurt anything. Good luck

tmoss · May 9, 2004

Look at the wiring diagram in this thread, it has the relay terminal numbers on it..........

http://forums.stangnet.com/showthread.php?t=461176

Input needed from someone familiar with wiring electric fans...

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