Vent window only works for a few seconds at a time / 73 Imperial

[Dirk]

A few days ago, my vent window motor suddenly stopped working. So I removed the engine and it seemed that the gearbox was stuck. I was able to solve the problem by cleaning the gearbox and at the same time I cleaned the motor and reground the carbon brushes.
Everything is now working again, but only for 3-5 seconds at a time. Then the motor stops and after a short wait i can start it again for a few seconds.
I suspect that this is an overheating problem. However, I have no idea about electric motors.

Any advice/ideas?

Thanks

 

[CBODY67]

Suspecting you also re-lubed the bushings in the motor itself, with a high-quality moly-infused lubricant?

Just curious,
CBODY67

 

[Dirk]

Suspecting you also re-lubed the bushings in the motor itself, with a high-quality moly-infused lubricant?

Just curious,
CBODY67

No. I just put normal grease in there. Can it make that much difference?

 

[Big_John]

No. I just put normal grease in there. Can it make that much difference?

It won't. I just use chassis grease when I've had them and power window motors apart.

You either have some sort of binding or maybe a bad switch. Take the door panel off, unplug the vent motor and apply 12 volts to the plug (negative one wire, positive the other) and see how it works. If it still acts up, it's the motor. If it works OK, then it's in the switch or the wiring.

 

[Big_John]

reground the carbon brushes.

It just hit me, did you radius the brushes where they rub against the commutator?

 

[Dirk]

It won't. I just use chassis grease when I've had them and power window motors apart.

You either have some sort of binding or maybe a bad switch. Take the door panel off, unplug the vent motor and apply 12 volts to the plug (negative one wire, positive the other) and see how it works. If it still acts up, it's the motor. If it works OK, then it's in the switch or the wiring.

I tested the engine when it was removed. So it's clearly the engine.

 

[Dirk]

It just hit me, did you radius the brushes where they rub against the commutator?

I sanded the carbon brushes with 400-grit sandpaper and then sprayed everything with electron spray. So the original round shape is still there.

 

[Big_John]

I tested the engine when it was removed. So it's clearly the engine.

My adventures with a power vent. Power Vent Motor- Anyone ever take one apart??

I'm making an assumption that they still used the GM motors in 1973 like they did in my '70.

 

[NY69]

I would take the engine out, test it again on the bench and open it up again to see what's happening inside.

I had the same thing happening to me on a window motor. A spring of the carbon brush had broken off, a few months after the rebuild.

Luckily it was the window motor of the quarter window, which is almost impossible to access. Imagine the disappointment if it'd had just been a door window motor that is accessible in 5 minutes...

 

[Dirk]

I would take the engine out, test it again on the bench and open it up again to see what's happening inside.

I had the same thing happening to me on a window motor. A spring of the carbon brush had broken off, a few months after the rebuild.

Luckily it was the window motor of the quarter window, which is almost impossible to access. Imagine the disappointment if it'd had just been a door window motor that is accessible in 5 minutes...

I must have taken it apart 5 times, but I can't see any defects. Everything looks fine but the problem remains.

 

[Dirk]

My adventures with a power vent. Power Vent Motor- Anyone ever take one apart??

I'm making an assumption that they still used the GM motors in 1973 like they did in my '70.

That was my instruction

 

[bigmoparjeff]

Some electric motors have a bimetalic thermal protector in them which can get too sensitive over time. I've had to solder the contacts closed to get the motor working again.

Jeff

 

[Big_John]

Some electric motors have a bimetalic thermal protector in them which can get too sensitive over time. I've had to solder the contacts closed to get the motor working again.

Jeff

I don't remember there being one in my vent motor. I have seen those in power window motors though.

EDIT: Never mind what I don't remember. There is one.

 

[Dirk]

Is that the bimetal?
Or does it have a different function?

 

[Big_John]

Is that the bimetal?
Or does it have a different function?

View attachment 688874

That is exactly what it is. I didn't remember that the vent motor had that. If I had taken that motor apart 40 years ago, I'd probably would have remembered that... 3 years ago? Not so much. Ahh the joys of the tarnished golden years.

 

[bigmoparjeff]

Yes, that's it.

You may want to try cleaning the contacts first with a very thin file or piece of sandpaper to see if that solves your problem.

The "nuclear" option is to just solder them together.

Another issue that I've been seeing a lot of lately is high resistance where electrical parts are riveted together. If you have a multi meter, you may want to do some point to point resistance checks on the path that the electricity flows through the motor. Ideally, all your connections should be less than .5 ohms. Any connections over 3 ohms is a problem that could be heating up when the motor runs.

Jeff

 

[Dirk]

That is exactly what it is. I didn't remember that the vent motor had that. If I had taken that motor apart 40 years ago, I'd probably would have remembered that... 3 years ago? Not so much. Ahh the joys of the tarnished golden years.

I know that
Memory and a thousand other aches and pains.

 

[Dirk]

Yes, that's it.

You may want to try cleaning the contacts first with a very thin file or piece of sandpaper to see if that solves your problem.

The "nuclear" option is to just solder them together.

Another issue that I've been seeing a lot of lately is high resistance where electrical parts are riveted together. If you have a multi meter, you may want to do some point to point resistance checks on the path that the electricity flows through the motor. Ideally, all your connections should be less than .5 ohms. Any connections over 3 ohms is a problem that could be heating up when the motor runs.

Jeff

I'll have another go at that. I had already used 400 grit sandpaper. But maybe I caused the problem in the first place.
I'm at war with multimeters and the like. I can't get to grips with them.

 

[CBODY67]

The "chassis grease" I use is Ford-spec wheel bearing grease for disc brake cars, which has moly in it. Currently have the synthetic version of that from Valvoline, in a grease gun cartridge.

FWIW,
CBODY67

 

[bigmoparjeff]

I've had a couple motors over the years that were just hopeless. Everything looked perfectly normal inside, but they would quickly get very hot, even running them with no load.

Jeff