Re: [atlas-craftsman IO] OT-how to test and repair DC brushed motors.

On 8/11/23 11:02, Bill in OKC too via groups.io wrote:

SWMBO' s power wheelchair lift crapped out the other day.
New motor is no longer available since the lift is
ancient. Manufacturer of the lift removed any OEM
markings. It's a right- angle gear motor, which I'll
eventually have some photos and dimensions for. This is
the in-and-out motor for a Harmar AL-600 lift that fits in
the back of a van. Near as I can remember it was made
about 2007 or so.

There is no continuity in the motor, but  othinf seems
burned. I pulled it apart and fiddled with it, and got
continuity back. Hooked it back up to power trying to get
a current draw reading and it spun up and  rapped out
again. No continuity again. Brushes look good.

Well, two possibilities.  One is the brush springs are shot
and don't hold the brushes against the commutator.  On a lot
of motors, if the copper braid that is supposed to carry the
current gets corroded, then the current goes through the
spring, that fries the temper.

This is fixable.  Amazingly, it has screw-in brush caps!

Another possible situation is there is an open winding in
the armature.  You can check for this by applying a very low
voltage, like maybe a single D cell to the motor, and see if
it pulses and pauses.  That is not really easy to fix.

That looks like a REALLY standard motor, but likely it has a
special shaft end with the worm machined into it.

Jon

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