I called the sellers of this fan and found the following:

It is two speed, controlled by a grey (low speed) wire and a brown (high speed) wire. If both speeds come on simultaneously it draws a momentary, whopping 60 amps. Steady draw for both is 29 amps. I had it wired with both coming on together before. It is designed to come on low speed at your specified setting and then high about 10-15 degrees above that. If things are designed well, high speed is seldom needed. The CFM of the low speed is 2000.

I felt prosperous enough to purchase a second thermostatic control for $18 at Pep Boys and wired it so it controls the high speed side separately. It does not actually seem to be needed this time of year. The low speed is set to come on at 205 and it pulls the temp back down to just above the 195 of the thermostat and then cuts off. All this just sitting idling in the garage. I do not know what the high speed side is set for at this point. It is just higher than the low speed. I will fool with the high speed side next summer I suppose when we get some 90-100 degree days. I know I could figure this out now, but it's on to other things at this point.

Here is the big news. The alternator keeps up nicely with the low speed side of the fan. It stayed above 13 volts the entire time. Also, there was little impact from the start up of the low speed fan. It seems that challenge has been dealt with and put to rest. Thanks again for all the feed back and suggestions when the car died about 6 seeks ago on the way to work. It seems we seldom take the steps needed to fix things until they really break down. So this failure was, for me, a bit of good luck. The car seems to be running better now than it has in a long, long time. Bottom line:
1. Better fan control and more stable voltage.
2. Better ignition with new VR pickup/
3. Better fuel table.
4. Better timing table.

I'm heading to the cruise this Friday once again!

Sam

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Good job! Happy this worked out for you.

Thanks. I figured you guys could use a dose of good news after all my complaining and griping the last couple of years.

Sam

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Great news! Enjoy the tuning and driving.

Lou

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Home of Slant6-powered fun machines since 1988

Wow, yeah, a 60A draw will certainly tax any but an industrial/commercial-duty alternator. Let's hear it for easy fixes!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Gotta love breakthroughs, eh?

If its a two speed fan you should never be using the low and high speeds at the same time. The high speed coil will get the fan spinning faster then the low speed coil would, so if you power the low speed coil all your doing is heating internals of the fan up and drawing excessive current for no increase in cooling performance.

Second thermostatic control? Why any thermostatic controls? If you have any spare outputs from the megasquirt you can use that to drive them (with a relay in the middle, of course).

Didn't you say you already ordered the alternator? Upgrading may still be a sound idea. IIRC your other alternator held up (even while you had the fan snafu) when it was cold.

I thought 2 speed fans were wired as

2 halves....


Either half is low speed.

Both together is high speed.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Here is a clue perhaps: The high speed will not work at all if the low speed is not turned on first. I did not try that. This is what the dealer said.

Sam

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Negative, unless we are talking about two separate smaller fans, fan#1 for low, fan #1 & #2 for high. But this isn't the case, its a single large fan.
Unless the fan has some kind of built in circuitry, that doesn't sound right. 3 total wires to fan, all thicker gauge right?

All motors have a startup current (peak amps it draws for the first few seconds until it winds up tp speed). Also called inrush current. Your "supposed" to start the low speed winding first, then transition to the high speed winding. The inrush current for the low speed winding is less. If the fan is already spinning, the inrush current during the transition from low to high is minimal. You should be able to go directly to the high speed winding but inrush will be substantially more. Fan doesn't care much either way, just makes it easier on the current draw.

Common ground.

2 different sets of internal windings for the motor.


The only way to get high speed is use both windings.


Either set of windings would be low speed.



I took a failed nissan 2-speed fan motor apart once (to see if it was fixable ....not) .

Had 2 sets of brushes on the commutator. Common ground on 2 of the brushes.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Perhaps there are multiple designs then. The fans I worked with (such as the ford taurus unit I once used) worked as I described.

Was that an older design? Usually you don't see high current passed through brushes any more.

We may be saying the same thing by different words. The point your referring to as a common ground - consider that the "center tap". If you use one of the far ends as a ground, the center tap would be low speed and the outer would be high. You'd just have to get the polarity right to achieve proper direction.

Not a center tap.


The brush pairs were about 90 degrees apart, not 180 like on a 2 brush motor.


Probably similiar to a 4 brush starter motor wiring.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Sam You could figure the starting temp of the high side to know for sure by blocking airflow. (ie piece of cardboard) Be better to experiment now than to find out is for NASCAR temps of 270+ degrees!!

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MRO....

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