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Old 01-11-2008, 08:14 AM
70 Chevelle SS 396
 
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2 speed cooling fan switch

So- I've decided to use the Ford Taurus electric fan on a project I'm working on; It's almost an exact fit for the radiator.

What I've been trying to figure out is how to make the fan operate on both speeds. I know I could use two temp switches/probes- one for each speed; But I wanted to minimize the amount of wiring and "extra" stuff in the engine bay.

SO! I've found a temp switch from a VW that I think will work. It was used on two speed fans on various models. I think originally the switch was wired with the power wire, or coil + wire for the fan relay. Since it's a bi-metallic switch, couldn't I use it as the coil - on my fan relays, and use it to trigger both the high and low speeds??

HERE is a picture of the switch.

There are a couple different temp ranges for this switch. One is first stage on at 185f, second stage at 199f. Another is on at 168 and 199.
Which would be the better of the two, for a 350 small block, mild cam?

Thanks!
Nooj

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Old 01-11-2008, 08:36 AM
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Sounds like a cool (no pun intended) solution. Use two relays, one for low speed and one for high speed. I would go with the temp sensor that has the higher low temp setting (did that make sense), as a SBC operates best at around 180-195.

One of those three terminals on that switch has got to be the common. The other two terminals are for low and high speeds. Run 12 volt positive to the common terminal then run wires from the other two terminals to the coils of two relays. Ground the other side of the relay coils. Now run a heavy wire (#10) from a fused 12 volt source to the normally open terminals of the relays. Run two more wires from the other side of the normally open relays to your fan low speed connection and high speed connection


Vince

Last edited by 302 Z28; 01-11-2008 at 08:41 AM.
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Old 01-11-2008, 08:46 AM
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Thanks for the reply. I'll go with the 185-199 switch then. I've got my relay wiring already planned out (thanks to AlanHorvath.com and other posts on this forum)- and yes, definitely two relays.

I'm not sure where I'm gonna stick the switch yet... It's an aluminum radiator, so I may have someone weld in a threaded port for it at the base of the radiator.

I'll let everyone know if this works out well. Hopefully it'll be a simple solution to using the 2 speed Taurus fan, without having to buy an expensive controller or two temp switches.
BTW- I've seen these dual stage switches online for $12 or so. Probably more expensive from the local parts store, but after shipping from online stores, the difference will be negligible.

Nooj
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Old 01-11-2008, 11:19 AM
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Yes, you can ground the common of the switch and hook it up that way also.

Vince
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Old 01-13-2008, 11:16 AM
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update: My dad and I went to Pull-a-part yesterday and there were tons of Taurus fans. Most of them were already removed from the car, from other people taking out engines or radiators. Got two of 'em- One was from a Lincoln though. We're just gonna use whichever one fits his radiator the best. The Taurus fan is almost an exact fit- so probably that one. Paid $13 a fan.

Also- I found my temp switch on a VW! Had a nice looking little electrical plug with it too. The best part is- they just gave it too us! Didn't even charge for it And yes, I made sure they saw it.
Sure beats ordering it from Napa. They wanted like $40 for it!

Anyways- hopefully soon I'll get around to wiring it up and testing it out. I just hope I got the right temperature range switch.

Later,
Nooj
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