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Posted by KenaiGary [65.74.48.28] on Sunday, January 22, 2012 at 18:31:53 :
Back in November, I posted about some heater issues I was having with my 61 WM300 on Gordon's site. I just posted the following there and thought I should post here as well as I'm certainly perplexed about the challenge I'm having. Photos of the various heater models are on Gordon's site as well as the full posting string, so I didn't think I would need to post them again here. Here's my post:
I finally found the time to order and install a new blower motor for my heater from VPW. The image shown in the VPW catalog didn't exactly match what I got, but I made it work to a point. My problem is that the fan isn't moving as much air as I think it should and know it isn't sufficient to keep the windshield defrosted since I drove it afterward.
Background: I believe I have a Model 79. It is not a Model 75 or 77 as posted earlier in this string. I've posted the diagram from my S Series Service Manual 1962, but it doesn't indicate the model. In reviewing my other manuals, I believe it is a Model 79, it is not a Model 83. The Model 75 has a fan and blower wheel while the Model 77 has a blower (mouse wheel). Mine just has a fan with set screw.
VPW sent me part #06:HM12V0811, which is the only one they have and it is different than my non-working motor. The part #in the WM300 service manual is: 1922703. The VPW catalog shows two long post terminals that extend into the cab and two short terminals that go into the heater frame, but the one they sent had two long terminals on each end. In order to adapt it to fit I had to cut the terminals that go into the housing or else the fan would not turn as it would bump the terminals. All went well with the install. I have three definite fan speeds, low, med and high, and the fan seems to spin at appropriate rpms at each speed, at least I think they do.
I tried adjusting the fan on the shaft and felt that the more it was inset into the housing, the more vortex it would create. That didn't seem to help so I reset it further out from the housing and that didn't make a difference either.
The Model 75 fan/blower unit looks like it would blow more air but I don't believe it will fit my housing.
Questions I have that I'd appreciate your input:
-Maybe the motor I purchased spins at a lower rpm than what I need?
-Maybe the shaft on the new one is spinning in the wrong direction, but I can check that out once I have some time to pull the unit again, but would appreciate it if anyone knew if this is a possibility.
-If it is turning in the wrong direction, can I reverse the wiring and connect the ground to power and power to ground and the shaft would turn in the opposite direction? One guy told me this, but I am hesitant to try since that seems like it could reverse the polarity and/or burn the motor out. The shaft does spin in either direction.
Also, is there anyone out there that rebuilds these motors? They appear to be sealed units, but there is an indentation that runs around the center that almost appears it might be serviceable. As you can tell, I am definitely not an electric guy, but I was proud I did the install and all seems to work well...but, not enough air blowing, which was the whole point of this exercise. Yes, I checked the air movement at the housing where the hoses attach and little air was coming out, and both hoses are clear with no holes or loose fittings.
The heater core does get very hot and that in itself warmed the cab up in -20 weather, but the defrost was not sufficient due to lack of air moving.
Thanks for any help, guys.
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