The Stovebolt Site Forums The Shop Area The Electrical Bay Heater Switch

I have the truck apart and decided to test the heater fan motor with the battery. The motor has two wires, I grounded one and used the other for power. I think that is the way that it was setup originally. I am not sure if the rotary switch goes between the power wire or ground wire.

The switch is a red rotary switch that I bought from one of the vendors. It matched the one I replaced it with.

Anyways. The switch windings in the back of the switch got red hot, lighting up like a light bulb.

Is this the way all the switches are or has anybody replaced it with something else? Did I connect the wires correctly?

TIA

Switches of any kind are inline of either your ground or your Hot wire, never hook them up to both hot and ground! you'll design a toaster!

Mark

oldbluetruck,

I would make sure the new rheostat and fan motor were rated for the same voltage as your truck (your battery). The rheostat would go in series on the + or supply side of the motor and the other motor lead would be grounded.

The switch should have an off position, as well as being variable. It will get warm, but I don't think it is suppose to glow like a light. Don't forget to put a fuse in this circuit...didn't some of those switches have one hooked on the back?

Stuart

that reostat switch will get hot...thats how it reduces the voltage to run on low speed... try it on hi and it wont get as hot.....

The motor may be a 2 speed motor & 1 wire is high & the other is low.It may be internally grounded. A hot wire off the ignition & with a fuse goes to the bat side of the switch. Try just one of the wires from the motor at a time & see how it works.

oldbluetruck,

I don't know what kind of switch you purchased, but this link shows what appears to be a stock switch...it has two HUGE resistance coils. Just for your info!

http://cgi.ebay.com/ebaymotors/55-5...206QQssPageNameZWD1VQQrdZ1QQcmdZViewItem

Stuart

the switch Stuart links is indeed the factory fan switch for 55-59, which will not get red hot, and should have those insulators on the resistance coils - one of the wires is probably ground if it's an original motor - if the resistance gets really red hot you may have a bad motor

Bill

Thank you for all the replies and advice.

What it sounds like is that the two wires are for low and high speeds and the motor is (may be) internally insulated.

1. So, the motor is grounded by the heater box, and

2. I have the wrong switch. The one I purchased from one of the venders does not have the insulator coils hanging out.

The motor is not the original. The original stopped working and when I took it appart there was a part that was broken so I went to a salvage yard and they had a motor that was exactly like that original and was 12 volt. I am using that motor. It was only $5.

I believe the motor will work for what I need. I just need to get the right switch. I thought that maybe a three speed switch was doable.

I am not close to being an electrician.

Could I use some other type of switch?

Thanks again,
Dennis

If the motor is a 2 speed motor you can get a single-pole double-throw toggle switch connect the hot wire to the center term. & the other 2 wires the the side terms. Seems like the switch you have should work if it is the right voltage.

oldblu,

I am not real close to being an electrician either, but I have been called a know-it-all, so here is my unprofessional, uncalled for opinion. I don't think a automotive device like a motor would be built to ground through the case.

I think one wire is ground and the other is power. I think the speed or speeds of the motor are determined by the voltage applied to it. If it is a two speed motor, the switch will have the appropriate resistor built in to reduce the voltage for the slower speed. That is why you see the large resistors in the factory switch in the link I supplied.

You are sort of dealing with an unknown...a $5 dollar motor you picked up at the salvage yard that looks the same as the one you took out of your truck!

I would think it much easier, from a manufacturing standpoint, to put the speed regulation in the switch rather than the motor. It wouldn't cost much to try wrenchbenders switch suggestion, and that might be the answer.


Stuart

Your 47 horn should not be grounded to its mount. It should have two wires; one to six volts and the other grounded when the horn button is pressed.

Jeff,

You are not starting trouble, you are sharing very good information.

I think the point I was trying to convey is that there will always be TWO wire attached to the motor. One might be hooked to the frame to locate on a grounded body component, but there will always be TWO. You will never have an instance where the motor frame must be in intimate contact with a grounded source for the motor to function. A wire will always be supplied that must be attached to a grounded point and another wire that is connected to a power source.

Wow, what a novel. So, in conclusion Jeff, I hope I haven't come across as argumentative as I truly value all input and try to respect every ones opinion.


Stuart

Hi Stuart, It's been too cold to work on the '38. I must disagree with you here though. The heater on my '38 has one wire. The frame is directly grounded to the body. As the old saying goes, never say never. My advise to the original poster would be to ground the case, touch both wires (one at a time) to a positive feed and see what happens to the motor's speed. If it turns on both, one faster than the other, use a three pole toggle or use the rheostat switch with the high speed wire.

Tiny,

Welcome back..I think you are correct about the one wire coming out of the heater, but I think it is the only wire you can SEE!

I played with the heater motor out of my 55/1st (6v?) before I wrote the post above. It indeed has only one wire coming out of the heater area...the OTHER wire, the ground, is a little short dude that exits the motor the same as the power wire, but, goes to a screw attached to the heater (ground).

On my old truck heater, this is all hidden in back where you cannot see it when the unit is installed in the vehicle.

Your advice about the "never" word is well taken, I usually try not to say it, and might has stepped on my toes on this wire issue.


Stuart

Admittedly I've not had the heater motor out of the housing on the 38 so I don't know if it has a "shorty" inside but I have had the defroster motor off and it has only one wire which goes to the switch. It grounds to the heater case which then grounds to the body. It's kind of hokey having two seperate switches to control the heater and defroster but it's better than my 55 1st panel was where both were on or both were off. At least on the '38 I can run only the one I need. (Today that would be both full blast!!)

Thanks again for all the replies and advice.

Original poster here.

What I believe that I need to do is ground the motor body and touch the two wires separately with power. That way I will see if it is a two speed motor or not body grounded. If one works and the other doesn't can a two speed motor be dead in one speed?

If this does not work then I will assume it is not grounded by the body and one of the wires must be a ground and the other for power.

If one wire is ground and the other hot will the motor reverse if I reverse them?

Can I screw the motor up by doing any of this?

TIA
Dennis

Some replacement type motors will reverse when you reverse the wires. Experimenting is the only way you will figure this out. It,s not likely you will damage the motor with short time hookups. If it would you probably already have.

Dennis,

A permanent magnet motor will reverse when you swap leads. These would be like the Grainger replacement motors some folks use in the heater.

The original motors were series wound motors...they won't reverse without reconnecting them internally. The starter is series wound. It won't start the truck backwards if you reverse your battery cables!!

I need to apologize for hijacking your original question...I really didn't intend on stirring up such a ruckus. I'm now officially a one wire guy!


Stuart

Series wound motors won't reverse if the wires are reversed, but often they will run faster wired one way as opposed to the other.

Just finished re-installing my fan assembly an hour ago. There were two wires coming from the motor and a label on the motor stating that the "orange wire is a ground and the black is power. If I want to reverse the motor I should just reverse the wires". I did attach the ground to the heater case under one of the screws which holds the core to the sheet metal. This is the way the unit was when I bought the truck. I had it apart because of a leaking core.

Welcome back...what did you finally do on the leaking heater core. It was the round one wasn't it. Yippee on the two wires. My '55/1st has two wires on the blower motor also!


Stuart

Hi atomarc - I've been here but on different other subjects. You are right. It is a round core. The repair shop called and said the core tested fine. I told them that in the past it ran fine for about an hour and then started to drip. The shop put it back under test for a few hours and discovered a pin hole which only showed up after a period of time. They soldered it and gave me a 6 month warranty on it. I ran it in position minus the casing for about 6-8 hours and it stayed dry.
So today I figured I should close it all up and get it running the way it should be. It was not a big job, about 30 minutes including draining the rad. Tomorrow I will test drive and pray that elusive drip does not come back now that I have it all buttoned up.
Bill

Update on the heater motor and switch.

Thanks again for all the replies, information, and suggestions.

I bought a switch off ebay (thanks atomarc) and should get it soon.

I also checked the motor. It has two wires and one if for ground and the other for power. I assume it doesn't matter which is which. It is a screaming motor at full blast.

Thanks again for all the information.