Possible Leak in Starter Circuit?

[Colonel Biggs]

I have been having an intermittent problem with a starter. One of the insulated brushes has lost some of its covering. I don't know whether this could cause an arcing when the starter button is activated. Sometimes I can get the starter to spin nicely on the bench; other times, just a spark at the terminal post. I have checked the field coil circuit, and there is no shorting there.

In running a continuity test on the two insulated brush holders to the end plate, one of them shows a reading of “9.5” on the 10K scale, and the other brush shows about "100" ohms on this same scale. I believe this amounts to 95,000 ohms in the first case, and one million ohms in the second? What I don’t know is the significance level of resistance readings of this magnitude. Since there is not supposed to be any continuity between the end plate and the insulated brush holders, I suppose that I should opt to replace the insulators for these four rivets before putting the starter back on the car.

If anyone has any thoughts on the electrical math involved here, I'd like your thoughts.

Gordon

[Tom Wesenberg]

I wouldn't worry about those readings. Do you have a picture or the end plate insulators?

Starters rarely have a problem. How are the brushes? Normally the ground brushes wear about twice as fast as the two insulated brushes.

[Colonel Biggs]

New brushes are identical in size to the existing ones. Plenty of spring pressure, too.

[H. L. Chauvin]

FWIW: There is a very small amount of clearance between starter rotating armatures & magnets.

Most Model A starters have been rebuilt many times in the past 80+ years.

Many rebuilders, (some in shops, some in kitchens under a kerosene lamp), cleaned & polished the commutators, verified continuity between segments of the commutator & segments of armature, removed & provided new brushes, checked for frayed wires & shorts, but never took the trouble to change out 80+ year old worn bushings which have increased wear from intense heat when starters were malfunctioning & dragging, & which later can allow the armature to get too close to the magnets.

With the inexpensive prices of both bushings, & brushes, I usually change both bushings & all brushes so the starter can last at least 40 years on a Model A.

I'll be sure to try to remember to let y'all know if it lasted this long in 2055.

[Colonel Biggs]

Sir Henry!

I fall into that category! (Except for the kerosene lamp part...) When I'm in Houston the kitchen is often the locale of such undertakings.

You are correct about the bushings, but in this case they are in good shape and there is very little end play. I do have a question for you with respect to replacing the insulated brushes. I am of the opinion that these are probably done with the field coils out of the housing. First of all, the access to the clamps (to which the brushes attach) is better. I believe that most rebuilders will first clamp the ends of the insulated brushes, and then solder the connection. Therefore, it almost makes it impossible to separate an existing insulated brush from the clamp with the field coils still in the housing. If you know of a technique for removing same while the coils are still in place, I'd love to hear it! I am leaning toward wrapping the exposed wire with some string, and using some super glue to hold it in place.

As always, your thoughts are greatly appreciated.

Gordon

[H. L. Chauvin]

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Hi Gordon,

Kitchens are wonderful working environments with coffee & snacks close by; even wine & beer to completely clear the frustrated mind during the toughest of endeavors.

After removing starter end covers, I always carefully used a propane torch at the proper angle to quickly melt the solder, then un-clamp the ends of brushes ..... next, clamp ends of new brushes & re-solder in reverse manner.

The Model A starter coils are made with about 5/16" wide & thick bands of metal wrapped with old cloth tape. If a this tape gets rotten & peels off easily, coils & magnets have to be removed for re-wrapping.

Called Scotch technicians several years ago -- they recommended Scotch Super 33+, which is performing well on my re-wrapped Model A starter coils today.

Removing coils should always be performed, (even on a kitchen table), by placing starter in a homemade wood vee block on a drill press deck, & then place screw removing tool, (flat head screw driver or hex allen wrench in drill press chuck), & unscrew same after soaking in Kroil. Old never removed side screws are always almost impossible to remove without a drill press.

Model A coils can stand this heat if the tip of the blue propane flame is low & held at the correct angle "away" from the direction of the coils.

After you do one, the next one is much easier; but take a break after the first one before it gets too monotonous.

Hope this helps.

[H. L. Chauvin]

Forgot to mention when re-soldering starter brushes to use what vintage gunsmiths refer to as “tinning” when soldering double barrels together on muzzle loading shotguns.

Place soldering flux on brush wire ....... then place flux on wire clamp.

Apply a small amount of solder just on the brush wire ……. then apply a small amount of solder just on the inside surface of the starter clamp.

Place “tinned” brush wire in the open “tinned” clamp ...... then close the “tinned” clamp on the “tinned’ wire.

Apply only a small amount of heat on this "tinned" connection, & the two will be joined together like a successful long enduring "vintage" state of matrimony ....... which is somewhat rare today.