Heater Motor

Steves46

Steves46

Well-known member
I wanted to check the heater and defroster on my 55 F100 and although the heater motor was turning between slow & fast, I could also hear thumping noise so I shut it off. :eek: The 20-amp fuse held but the wire was warm. I am still running a stock 6 volt system.

Time to pull the motor and take a look at what's going on but since I have never tackled something like this before, I would like some guidance. I checked the wires going to the motor and the connection and ground wire on the firewall. They look new to me; even the back of the heater motor from the firewall looks so clean. Is there a way to pull just the motor without having to drain the system? Thanks.
 
The heater motor is fastened onto the heater with 5 screws.To get at these screws you will have to drop the heater .If you have a block shutoff on the heater line just turn it off and drain the heater core itself and the lines .If not you will have to drain the entire system.I changed to 12 volts in my 55 and am going to install a Mohave universal heater from Speedway Motors when time allows.Good luck
 
its possible the squirrle cage has come loose and rubbing the inside of the heater when you get it out get some lite oil on the back and front bearings, the motor should turn easily with your fingers, the motor is probably dragging because of lack of oil, that will cause the wires to get warm
 
I was able to remove to motor this evening and everything looked pretty clean to include inside the compartment. I spun the cage fan and it made a few rotations. After oiling the shaft and letting the oil run into the bearings (there was no removal cap in the back or anywhere for oil), I spun it again by hand and it already seemed to spin with ease. I took it to my bench and put 6 volts to it from a spare battery and the cage rotated really good and quiet...no thumping. Installed it back in the casing, buttoned everything up and turned on the switch....nice quite motor on both low and high speed. Of course, high speed with 6 volts isn't that much! The only thing that still has me puzzled is why my wire going to the switch and my in-line fuse holder is still warm??? All wires going to the heater I believe are either 12 or 14 gauge and the ground is good, clean, and tight. I am using a 20 amp fuse. Maybe the amps this motor draws may create a little warmth in the wires.
 
The draw from the motor should be about ten amps, You might want to check it to see if it's any more than that.
 
Merlin, in the event it is (I think it's more like 15 to 20) does that mean the motor is almost shot? Also, where is the correct power source that the heater switch should be wired to?
 
According to my manual the power runs from the ignition switch through the fuse block to the heater switch and then to the motor. If you have more than a 10 amp draw I would think it's due to age of the motor and it might not be long before it goes.
 
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Merlin said:
According to my manual the power runs from the motor through the heater switch then to the fuse and from there into the ignition switch. If you have more than a 10 amp draw I would think it's due to age of the motor and it might not be long before it goes.
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i think thats wrong, the fuse should be in the line before the motor, that way it will blow the fuse in case the motor locks up and burns the wiring harness

A BIRD IN HAND IS WORTH MORE THAN TWO IN THE BUSHES
 
Thanks Guys. I think I discovered the root of the problem....I have a 12 volt switch not the correct 6 volt (which appears to be hard to find). I just bet the heater motor is 12 volts as well. Although it spinned pretty fast when I put 6 volts to it from a spare battery, I still didn't think it was fast enough to generate any significant air through the ducts. When I removed it the first time, I did not see any markings but what I may do is remove it again and place 12 volts on it and see how it behaves. I would however would like to determine if the motor is 6 or 12 volts.
 
Got a new 6-volt universal motor from LMC Truck but have one question; if I am looking at the squirrel cage with the motor behind it, what direction should the cage turn when power is applied; I think it should be counter clockwise. Apprecite if someone could confirm. Thanks.
 
Steve, I'm shootin' from the hip here, but I think the cage should turn in the direction of the slanted lower portion of the fins in the blower cage. That allows the blower to pick up air from the center and blow to the outside of the cage.

Why are you working on a heater in Florida? :D
 
Thanks "40." I figured it out and got it working. Yes, it seems silly working on the heater but the defroster will sure come in handy if I get caught in rain. Just trying to get all the bugs worked-out before the truck's first road trip to the Moonshine Festival in late Oct.
 
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