Re: [SilverStreak] Electronic Jack

[<waymark1@xxxxxxxx>]

Joan,

When brushes are almost worn out, if they have a positive stop and will
not wear clear to the wire, they will damage the commutator by arcing. So
it's very important to change the brushes at the first hint of poor
contact. I have saved a couple of starter motors by changing the brushes
before you have to bang on the starter to get it to work.

If your power jack is the same as mine (Reese) it has a recirculating
ball nut on the jack screw, which makes it able to operate with a
relatively small motor and reduction gear. So easy, in fact, that it has
to have a brake that goes on when the motor is not running to keep it
from lowering. This is why no oil is to be poured into the jack - it can
make the brake slip and let the jack lower under the tongue load. Heavy
oils can make the slip (overload) clutch slip too soon, too.

If the motor just suddenly quit with no warning you might have a bad
switch. The switch on my Reese jack looks like a generic rocker type.

Worn out brushes typically cause intermittent or weak operation. Also
brush wear particles can build up in the commutator gaps, which short
circuits the adjacent segments one at a time, making the motor weaker and
weaker. Such particles can be gently scraped out with a hardwood
splinter. Be careful not to damage the commutator.

"However, carbon brushes are soft and easy to modify their size to fit." 
With a file, or grind them down on a piece of abrasive paper on a flat
surface. Just get new brushes a little larger than the originals and
grind them down to slip easily into the brush guides.

"There should be less than 10 ohm resistance from the motor housing to
the battery negative terminal."
This is all solid steel as the jack is "grounded" to the A-frame, to
which the battery negative cable is fastened. Any significant resistance
should be fixable by taking the jack off the A-frame (support the A-frame
with a jackstand or hitch it to a vehicle) and scraping and wire brushing
all the rust from the A-frame where the base of the jack attaches, and
from the mounting flange of the jack. The battery negative or ground
cable/strap attachment point is another place that corrosion can make for
poor contact, so it may need to be removed and wire brushed clean.

I've had hard-to-get and extremely expensive alternators and starters
rewound and repaired by a starter-generator shop with good results.

Al