generator problem and third brush

[tcslr]

the ammeter is showing a steady - and constant discharge of 6 on the scale.  this is insensitive to engine speed.  same as idle, fast idle, and fairly good rpm.  I tried to increase third brush - no changes.

Can someone help me on possible next steps?  getting frustrated

 

[Bloo]

It sounds like your cutout isn't pulling in. That could be the generator's fault... or not.

 

What car? Is there just a cutout or is there a regulator too? Is it a Chevrolet? How many terminals on the generator?

Edited September 10, 2021 by Bloo (see edit history)

[tcslr]

its the Chrysler.  Just a cutout.  I tried tapping it.

[Bloo]

I would run the engine up to something higher than in idle, and then measure the voltage from the generator output post to the generator case. If it comes up anywhere close to 6 volts it should be pulling the cutout in. In that case I would guess a problem with the cutout. If the voltage wont come up I would suspect a problem with the generator.

[Rusty_OToole]

You should be able to bypass the cutout with a jumper wire. This will tell you if the cutout or generator is faulty.

[Frank DuVal]

Just do not leave the jumper wire connected when you shut off the car and leave. It will run the battery down.

[Bloo]

And possibly damage the generator.

[DFeeney]

Am I correct in thinking a stuck closed cut out contact ( or jumper wire left on) will allow a flow of current backwards from the battery to the generator armature/ground  with no resistance.  This would be the same as putting a metal coat hanger across the battery terminals.  The high rate of current would burn out /damage items in the circuit.  Just think 'in

[Rusty_OToole]

There is a lot of resistance in the field coils. You won't burn anything out but you will discharge the battery.

 

The field coils are energized all the time the car is running and it doesn't hurt them but at the same time the generator is charging. The purpose of the cutout is to turn off the current when the car is not running, saving the battery.

Edited September 13, 2021 by Rusty_OToole (see edit history)

[DFeeney]

Thank you Rusty,, I am becoming a more learned person by listing to people with greater knowledge than mine. 

[trini]

Clean and re tighten the battery ground, You may be surprised. Wile the engine is running remove the cutout cover. The contacts should kick in. If not, with the engine running use a voltmeter . One end to the GEN output and the other to ground . You should be getting about 6 vols or more. If you are OK at that point Keep tracing forward. If not ground the GEN field wire. If the mechanicalls in the GEN.is in working condition the voltage will shoot up. If not there is problem in the unit itself. ( brushes not seating/ worn/filing from the brushes causing short circuits, and many other things could be wrong. 

[chistech]

You can also test the generator by loosening the belt and putting 6v to the post. If the generator turns (it’s actually a DC motor) your generator is most likely working correct 

[trini]

chistech you are correct In some applications the generator works as a starter and generator. Remember to polarize the field 

[Bloo]

I won't speak for chistech, but I think he was just referring to running a dedicated generator as a motor to test it, rather than a starter-generator. It was a common way to test generators in the old days. Unless I lost count we are now up to three test methods for generators in this thread. Any of them will work fine.