Mark VIII fan speeds

[gmachinz]

Does anybody know which of the three terminals are for what? -G

[gmachinz]

Maybe I should have done a call-out to Camaroboy or Jody! I need to know how you guys wired your Mark VIII fans using the three prong connector affixed to it. I know one is a ground (which one I don't know yet) but are the other two for different speeds? Thanks for ya'll's help on this one! I have mine ready to go except for that. I did need to trim about an inch off the lower radiator support to set the fan down flush with the top of my upper radiator support-all that is left is to make my own aluminum mounts and I'm done! I can't wait!! -G

[derekf]

Erm.

I don't know, but I did find this on the Old Site:

Tony C
Unregistered User
(6/30/04 8:57 pm)
Reply Mark VIII Fan wiring help
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I just received my Mark VIII fan and noticed the plastice end where the wire connection would originally connect to has three prongs inside. Which prongs are used in wiring the fan? I hope I explained myself correctly.

Tony C.

camaroboy69
Registered User
Posts: 1293
(7/1/04 7:32 am)
Reply
Re: Mark VIII Fan wiring help
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If you look at the white part it shows a + and a -. Very easy to wire.
Adam

Hopefully this is helpful, at least a little.

[gmachinz]

I guess if I were to have looked a little closer I would have seen the - and + terminals! Anyway, what's the deal with the center terminal? I just conected it briefly to my battery to see how the wiring checked out and it almost fell off my radiator support! I was holding it up with one hand while I ran the connections to the battery junction. That thing MOVES! I just checked the price on the Hella 70-amp relay I was going to use-it's gonna run me about $30-but it incorporates a tamping diode so that makes it worthwhile to me. -G

[GO67SS]

How much do those MK fans run?? Do you have a diagram of how you are wiring it in?? I have my SPAL fan hard wired in to my LT1. An would love it to run on a relay and temp.

Thanks

[CarlC]

Remove the inspection plate on the motor next to the plug. You will be able to see the wiring connections. On most MarkVIII fans, the center terminal is dummied allowing for only single-speed operation.

I sodiered a diode across the + and - terminals inside of the inspection cover. A 50 cent diode + $13 70-amp relay did the trick.

[gmachinz]

I am still at odds as to go with either a thermostatic type switch w/probe or a traditional single pole switch. As for the wiring, I have a +12v junction on my radiator support with an 8 gauge wire running to it form my alternator charging post. From there I ran the same gauge wire to the #30 pin on my relay with a Japanese style 50-amp fuse inline. Pin #86 is my ignition turn-on lead with a 20-amp fuse inline. Pin #85 on the relay goes to the thermostatic switch and #87 goes to the fan +12v. The Hella relay has contacts made from Silver-cadmium oxide which should last forever and the one-way diode feature insures no spikes or "momentary turn-on" situations. -G