2 speed electric fan: broken, or am I doing something wrong?

[BerniniCaCO3]

this setup:

http://www.fordmuscleforums.com/cooling-articles/494753-two-speed-variable-taurus-fan-control-panel.html

Let me know if there are any flaws/ bad design there, and I'll reconsider!

I tested the resistance, I think I've got a single-speed fan, resistance is the same on both hots, which explains why I couldn't tell a speed difference.
I've gone ahead and ordered a new fan motor, rf64 (or pm9032- but that was going to take longer to arrive), which should be 2-speed. Hey, and then I'll have a new motor. I only paid $20 for the fan at the boneyard anyway.

[BerniniCaCO3]

it came from a 1993 mark viii. According to some people, single speed mark viii fans are out there, this must just be one of them.

[gadget73]

my mark 8 fan had 2 speeds, but be damned if I could tell any difference. Perhaps its just one speed with two seperate inputs. If thats the case and you can power both without it doing bad things, it simplifies the circuitry. Some fans you cannot power both + leads at once.

[1987cp]

this setup:

http://www.fordmuscleforums.com/cooling-articles/494753-two-speed-variable-taurus-fan-control-panel.html

Let me know if there are any flaws/ bad design there, and I'll reconsider!

I tested the resistance, I think I've got a single-speed fan, resistance is the same on both hots, which explains why I couldn't tell a speed difference.
I've gone ahead and ordered a new fan motor, rf64 (or pm9032- but that was going to take longer to arrive), which should be 2-speed. Hey, and then I'll have a new motor. I only paid $20 for the fan at the boneyard anyway.

Oh, variable controller and two relays doing the same job for high speed. Funky.


FWIW, Thain, on my Tortoise fan there's a very marked difference between high and low. Haven't bothered to make any measurements of any sort, but it's probably at least half again as fast on high speed. I'm pretty certain the draw is over 30 amps, since it cooked a stock Windstar SPDT relay that I determined to have been a 20/30. Now I have a 40A SPST or on/off and a 30/40 SPDT for high/low with a 40A fuse protecting the lot.


OP, if you seem to only have one effective speed, and are willing to spend the $$$ on a variable controller (Hayden's is $100ish, DC's is supposed to be much more reliable at about $150), why not do only that? Hook it up to whichever side is functioning as high speed, and it'll ramp the speed up as needed, rather than the constant on/off cycling I get with my $14 temp switch.

[BerniniCaCO3]

already did: the flexalite shown there.
Trouble is, it has a 30 amp fuse, this fan draws 60 amps.
The idea was to use the variable on the slower rpm circuit, then have the on/off $14 switch just for the high speed when it becomes necessary.

Just received "RF64" in the mail, the ford fan, and turns out-- it's true single speed. Whoops-- guess I do have a 2 speed fan. *sigh*.

I've already spent the money, I'd like to use the variable controller, so I'll probably keep the 2 speed fan and use resistors to bring the 2nd circuit down in amperage draw, being careful of course to find resistors that can handle 30amps.
Or use the single speed and cut it down in a similar fashion.

[gadget73]

you need huge resistors to do that. They'll dissipate so much heat that its not even funny. Power transistors to drop the voltage without so much heat are a better idea. Thats actually how the variable speed controllers work. Mark 8 fans also draw about 40 amps, not 60.