Need HELP wiring a fan?

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Need HELP wiring a fan?

Postby sparkknock » Fri Apr 13, 2012 11:25 am

hey i picked up a fan at a swap meet and want to wire it up.
i want to just run a wire from the battery to a switch to a light to the fan but im sure theres more to it?
i noticed when u buy a kit it will come with relays and such so i have a feeling im doing something wrong so,,,,
whats the most simple way to do this on a h-body? i have a real hard time with electrical and im color blind!
it would be nice for it to work automaticly when it gets hot but neccesory, i would like a idiot light on the dash to tell me its on n off?
i did read another post but got so lost on what they were doing because i did not have all the parts from there kit that they were talking about?
can someone help me see the light? (to he fan) :think:
thanks spark
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Re: Need HELP wiring a fan?

Postby stage169 » Fri Apr 13, 2012 12:29 pm

Spark, looks like some fans can pull 20 amps so if you used a switch it would be a hog :D It is better to let a relay switch high current like that. Most accessory switches would work fine for turning the relay(s) on.

For your fan circuit you could come up with a lot of different ways to wire it. Relays aren't expensive and if a yard is close you could snag some for cheap. I know some of the H body rads have a spot for low coolant you might be able to put a temp switch there if that is something you want to do. The most simple way? I'm not sure but here are some schematics I've saved just for ideas. Brian
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Re: Need HELP wiring a fan?

Postby SunbirdMan » Fri Apr 13, 2012 2:46 pm

Depending on the fan, the wiring and relays may need to upgrade.
One example:
"The Taurus fan pulled a little over 130 amps on startup (only for milliseconds) and settled down to right around 40 amps using the high-speed wire."
Roger---------------------------------------------------------------
UNLESS OTHERWISE SPECIFIED
DIMENSIONS ARE IN INCHES
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Re: Need HELP wiring a fan?

Postby sparkknock » Fri Apr 13, 2012 11:05 pm

HEY THANKS A BUNCH BUT HOW DO U TELL WHAT TERMINAL IS WHAT ON THE RELAYS?
AND ARE THE RELAYS MARKED HOW MUCH THEY CAN HANDLE?
SPARK.
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Re: Need HELP wiring a fan?

Postby stage169 » Fri Apr 13, 2012 11:48 pm

These relays are standardized no matter the manufacturer they are almost exactly the same. Most of them have the terminals labeled (30, 85, 86, 87, 87A) and are physically just like the schematics I posted.

Check out the pic "How it Works" and towards the bottom it says 20 amps on the NO (normally open) contact for inductive loads (like a electric fan motor).

If you can go to a yard you will see them in a ton of cars. If you look a little closer you will see some just for the stock electric fans. You might luck out and find the relay that is good for 35 amps NO (see the pic "Cooling Fan").

You can always double up the 20 amp relays for one big cooling fan like the schematic shows in the pic "Cooling Fan".

I know that if you are not familiar with them it may not seem worth it but if you get a chance to see one it will make sense. I've even used a small 9vdc battery with the negative terminal to the relay terminal #85 and the battery positive terminal to the relay terminal #86 to turn them on. You will hear the relay click. Hope that helps. Brian
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Re: Need HELP wiring a fan?

Postby firebird77clone » Sat Apr 14, 2012 10:15 am

You can wire it straight if you like.

Use 10 AWG stranded wire. Use an appropriate size fuse, placed near you source ( positive battery post ). Run the wire to the dash, and to a heavy toggle switch. Wire your indicator lamp directly off the switch, and to ground. The switch also feeds the fan, which also goes to ground.

It's simple, but the extra work to wire in a relay with a temperature switch would be well worth the effort
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