I have an old under dash AC evaporator unit I am going to install in my 76 D100. Unfortunately, the motor for the fan is rusted up solid. I have removed it and begun separating the housing.

Is evaporust safe to use on electric motors? I would like to dunk the whole motor assembly and remove the rust that way, if possible. Anyone tried this?

That's a really interesting question. If things wind up "no" by whatever route, you can probably find a replacement.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

According to the info on the bottle, it technically isn't 'unsafe' for electric motors. The composition of Evaporust is such that it only affects iron oxide (rust). It does not affect plastics, paint, or any of the softer metals. The biggest problem I see is that you would still need to clean and lubricate the motor. I feel it would be so much simpler to just replace the 42 year old motor and be done with it.

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-MattMan
LEANED & MEAN

I agree. I have looked everywhere, including Evaporust's website, and I can't find anything that says Evaporust can't be used on an electric motor, but neither have I found an affirmative statement that it can.

Last night I got the armature out of the housing with a little bit of persuasion from a hammer. This must be a really cheap motor because it doesn't use bearings. Instead, there is a ball on each end of the shaft that clips into a cup on each end of the motor housing that most likely held grease at some point in the past. Given that currently the motor is junk, I am going to go ahead and take a chance with the Evaporust. It can't get any worse, and I can still try and find an new motor that will work with the squirrel cage fans and housing on this unit. It looks like this AC evaporator unit might have come from a car that was flooded because the motor housing has some serious rusty crust on what would have bene the lower 1/3 of the housing if it was installed in a car. I don't think condensation from use would cause that kind of rusting.

I guess I will stick the armature in my drill press and give the bars a light cleanup and police with some sandpaper then blow it off with compressed air and dunk it in the Evaporust. Chances are if this motor isn't dead already I will kill it, but it might come back to life.

Aw, man, why did you have to post that link, Dan? Now I have another toy catalog to drool over! Seriously, though, thanks. I think I already found my exact same motor in that catalog. I will still try and resurrect the crusty original motor, but it is nice to know I can still find a new one.

OK. The motor is fully disassembled and soaking. Turns out the jug of environmentally-friendly deruster I had is Metal Rescue, not Evaporust. I bought it in 2012 so my memory was foggy. But they appear to be very similar products, so I am forging ahead. It is supposed to soak at room temp (68 F or higher) for a couple hours, but my garage is about 50 degrees during the day so I will leave the parts in there for a few days.

Here is a picture of the disasembled motor. I tested for resistance and continuity across all the bars of the armature (I hope I am getting the terminology right) and I believe I tested correctly. Testing the commutator bars 180 degrees apart revealed 0.2 ohms on every pair. None of the commutator bars was shorted to the armature. I tested the windings in the housing and none shorted to ground, or to each other, and all showed different resistance readings. I think this means all the windings are OK, the unit just needs to get derusted, lubed, and reassembled. Fingers crossed! Once the parts come out of the bath I will rinse, blow dry, and then cook in the oven for a bit to dry out the windings.

Interestingly, there are no permanent magnets in the motor. It appears the magnetic fields are created by exciting the windings. Of course, I haven't taken any electronics course since high school, and that was 23 years ago now. I vaguely remember something about Mr. Ohm liking square pie, but that's about it. I think I have messed up my old mnemonics.

Most small motors like this don't have permanent magnets (or at least didn't back then; maybe some of them are PM type motors now).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks! I was always interested in electronics but wasn't able to pursue that interest after high school. I don't know much beyond the rudimentary basics of DC and AC. I thought motors needed permanent magnets. Or at least that is what I remember from building model motors in auto shop and electronics shop in high school. I need to dig out my old Forest M. Mimms, III books and brush up on my electrical theory.

I guess I will find out in a few days if my rusty knowledge is enough to get this motor running.

I suspect that the "balls" in each end of the housing are the bearings. they are called (among other things) sleve bearings and often were sintered metal with lubricant forced into the voids. Common on small motors, including many starter motors.

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Dave

1977 d-200 crew cab ex-army pickup wants it's /6 back
1962 Valiant 2 door, 170, three on the tree
1972 d-100 parts truck
80 volare wagon now a parts car

Thanks for the info! Any lubricant that was there has long since dried out. I was planning on some dabs of wheel bearing grease unless anyone has a better suggestion.

See if the evaporust works on that.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 225 nitrous
64 Valiant Signet
64 Valiant 4dr 170

If only...

UPDATE!

Metal Rescue IS safe for dc motors! I got the motor cleaned up and reassembled and hoked it up and it wanted to turn. The problem is I mangled those swedge bearings unknowingly when I reassembled it. If I can find a source for new swedge bearings I can pop those in and this motor I think will be good to go. But I am betting that those bearings will be hard to find.

Wheel bearing grease is much too heavy/stiff for this application. Isolate those sleeve bearings to the maximum possible degree, assess their state of wear (should be very, very, very minimal sideplay with the shaft installed) and if that's the case, drop the bearings in hot synthetic motor oil for awhile, 5w30 is fine, then remove the pot from the heat and let the oil and bearings cool down together to draw oil into the pores of the bearing. Then wipe up and reassemble.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

See if any of these sizes are compatible. Rulon-J is a miracle material for plain bearings like this. No oil needed, ever.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.