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I have a '53 truck, 12 volt system, with original recirc. heater. Last winter I burned out the original 6 volt heater motor, and installed a new 12 volt motor from Chevy Duty. Now, this thing barely puts out any heat. It seems like the motor is just not spinning fast enough to move a sufficient amount of air. I've ruled out the switch by wiring the heater directly to power via a 110 volt household switch. The result is that when the temperature is much below freezing my heater can't keep the cab comfortable, and the defrost is totally lame. So, has anybody experienced this with replacment heater motors, and is there any way to make the darn thing spin faster?

Tyler,

I'm not the heater expert but have a few thoughts. Are you sure the rotation of the new motor is proper for the pitch of the old fan blade? If the new motor were to turn in the opposite direction it seems like the air wouldn't blow over the core.

The next thought would be that the motor and fan are fine but that the problem is with poor circulation to the core or through the core itself.

Does your truck still have a thermostatic valve still in the loop? Is it open and clear...could a hose be collapsed or the heater core plugged with junk.

If this problem came with the new motor, then it's probably the culprit. Keep us posted.

Stuart

Stuart,

Thanks for the thoughts. I'm pretty sure the motor is spinning the right way- it is blowing air out the outlet, just very weakly. I know the core is getting plenty of hot water because the case gets nice and hot when the engine warms up, and I know the airflow is clear.

The problem simply is that the motor doesn't blow enough air for my satisfaction. How can I speed up the motor without replacing it? Is this just the way replacement 12 volt motors are?

I would first check the connections. Make sure you have a good power connection and ground. If that doesn't fix it I'd have a pow wow with Chevy Duty. The motor could be bad or made for a different application. It could be made for a squirl cage fan instead of regular blades.

you gave the answer to your problem in your question, you took a 6 volt motor out and put in a 12 volt motor. at high speed the motor is only running at about 1/2 speed. you need a 6 volt motor or convert to a 12 volt system.

Tyler ,
You state you are running a 12 volt sytem in your post so that rules out it running half speed as posted above .
I installed an after market heater in my 52 ...I am thinking it is in your switch , you stated you have it hooked up direct with a household switch correct ?
Even on my brand new heater the switch has a reostat to control the amount of voltage or amps goin to the motor ..maybe try a new 12 volt multi position switch "low/med/hi" an see what happens ??ya may not be deliverin the proper current to operate the motor at its desighned potential
Just tossin an idea out.
Hope ya figure it out !
Tim

Re-read his post. It's already been converted to 12v.

It's the voltage that is determining the speed of the motor guys. That’s what the switches are doing, adding voltage dropping resistance to the circuit.
Without actually measuring the flow, how much air is being moved is highly subjective and simply subject to what an individual is used to. So if you’re expecting the AD fan to move as much air as your 2007 Chevy truck forget it. My truck, a 1950 stock 6v fresh air heater has a rebuilt switch, a too hot to the touch coil, new water and air hoses and it delivers just enough air at the defrosters outlets to keep the frost off the window. There isn’t a lot of air moving around there. I’ve not had any problems driving down to temps below freezing.
Denny Graham
Sandwich, IL

Be sure the motor is getting a good ground is the first thing, second, get rid of the 110V house switch. Make sure the motor is wired correctly, some have two power wires ( high & low ) and ground through the case. Did you bench test the motor? Any good 12v fan should blow really hard on high, how do you regulate the speeds? All heaters should have a 2 or 3 speed setting? Call the vendor and ask about wiring the thing, and go ahead and get a good switch while on the phone. Joe

I apologize, I did miss the part with the 12 volt system. I would assume the other motor {6 volt} ran at twice the speed a {getting 12 volts} and probably burned up in the process. Did the 53 have the resistors in the plenum box. I wonder when the other motor went out if it burned up the resistors. denny is correct about the voltages, if you had a volt meter it would make things easier, you could actually see what voltage you are receiving at the motor.

Yes, it is a weak blower, I think by design. Mine works fine, but does not blow real strong. I think if you want a more effective heater, you'll have to go to a universal aftermarket heater. They start at a little over a hundred bucks.

The Harrison heater in my 38 blows strong and will run you out on high with both heater doors open.

First, make sure that the squirrel cage is on correctly with respect to the fan housing. If I recall correctly, think of each individual fan blade as a scoop, which scoops the air from the center of the fan and flings it to the outside.

The fan motor has to run in correct direction. The fan 'flings' the air out and the rotation must match the housing. If the fan housing is shaped like a '6' (the outlet is the tail of the 6) then correct rotation is clockwise. If the housing is shaped like a 'P' then the correct rotaion is counter clockwise. I think (without going outside and looking) that the deluxe heater on my 51 has a housing shaped like a P, so the motor must run CCW.

I found all this out the hard way. I made sure I had the fan blade installed correctly in the housing and connected the motor leads only to find fair air output on heat and very scant output on defrost. I put up with this for a couple winters until one day I noticed that the fan was running the wrong direction. I switched the wires and my airflow doubled, at the very least.

Good luck!