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1938 Heater Defroster Fan wiring ?


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My '38 Special is equipped with the GM Deluxe Heater Defroster. My problem is that someone previously messed up the wiring. So the heat defrost fan was not actually hooked up. Would appreciate any help in sorting things out.

1st - where should the fan switch be located?

2nd - what should the switch look like? (toggle/slide/rotary?)

3rd - does the fan always run in one direction? or one way for heat and the other way for defrost?

I've also been looking for the engine # - can't find - where should I be looking?



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im not sure if its the same, from many pictures ive seen, there are different heater setups, one being the fact that youve got this defroster item. mine has the bent up sections of the dash for defroster air to flow if it had the defroster, but it only has a normal heater. the switch for mine is under the dash, near the parking brake, and is basically a lightbulb socket with a small light bulb that turns and had four positions it stops at, off, then 3 fan speeds, and the bulb is brighter for the higher speeds.

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Definately a different setup.

Since my first post, I've been successful in getting the fan motor to run. That was a challenge since there are 3 leads from the motor, one that provides power to create the magnetic field, and the other two - one for power the other for ground. (these two need to be reverved to make the motor spin in oppose direction.)

Note that this unit has 2 (two) fans attached to the motor. One a bladed fan that would blow heat thru the heater flaps. The second a squirrel cage fan in the housing with the tubes for the defrost. I may be wrong. But I've convinced myself that the fans spins one direction for the defrost, and the opposite for heat. You only get the benifit of one at a time.

Believe only one speed, spins fairly slow even with full power.


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The heater you have is not the type that was an option for Stateside Buicks. God knows what they offered up there in the Great White North.

"Can ya put a fireplace in it eh?


Hows about a wood stove then eh?"

Two hot water heaters were offered down here in civilization, the Master($11.95) and the Deluxe($16.75) One hot air heater($18.00-$26.75 depending on car model) was offered for very cold climates.

That's in American Dollars.

The Buick heaters have one or two motors. One for just heat, or one for heat and one for defrost. Each motor only uses one wire. The switches are rotary rheostats, the one for the heater motor is as ZondaC12 describes. The rheostat for the optional defroster motor is very similar but smaller. Both light up. Both switches are mounted through holes on the lower lip of the dash, on the left side of the steering column.

The engine serial number should be on the right side near the front.

There are many helpful articles about McLaughlins in the 1937-1938 Buick Club magazine, "The Torque Tube" a bimonthly publication.

Join the club eh.

[color:\\"red\\"]1937-1938 Buick Club

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wow nice bit of info there!

nice job with the canadian humor!

did you ever see the pictures i first took of my car, of the interior, back when it was in the garage, its a round, brown enclosure, my heater, with two doors that are half-circles and the outer edges swing towards the middle to open them. do you know which one that is? im guessing its the normal one (master?)

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Zon, The DeLuxe heater has the water pipes on a vertical line.

The heat output fot the 37 DeLuxe heater has been increased due to a new type of radiating core. This construction provides a large radiating surface in a small amount of space and increases the efficiency of the blower fan.

The Master is about 15% lower in heating capicity than the DeLuxe. It is round in shape but uses a conventional flat core. The Master is designed for use in coupes or in larger cars where the climate is mild. This is from a 37 shop manual but should apply.


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Today I finally got the unit assembled and in the car. I was then able to determine that the unit blows air both to the windshield and interior while spining the same direction.

Heated air to the interior and interior temp. air to the windshield.

Crazy thing draws more than 15amps, had to go with a 20A fuse to keep it from popping.

- Edward

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  • 1 month later...

Interesting discussion. I just went through my deluxe (stateside) heater and defroster this weekend. As previously explained, the US version (with optional defrost) had two motors - one for heat and one for defrost. My airflow was quite low, so I pulled the motors and cleaned up the commutators, then reassembled. Airflow now is about twice what it was. Still not comparable to a modern vehicle, but I wouldn't expect it to be. Each motor draws about 2 amps.

Your 15 amp comment is a bit of a concern. My local motor expert just sat down and said "very bad" Take that for what its worth, he's a Packard guy.

You may want to look for a short to ground.

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