Generator Issues

[DonaldSmith]

The generator on my DeSoto hasn't been charging. Nothing on my amp gauge, and the battery was run halfway down. I tried the grounding-the-field trick and nothing.

(I suspect that the recent zapping of the system with 12 volts to start the car didn't help. I had mentioned in a previous post that DeSoto grounded the starter solenoid through the armature of the generator, to prevent engaging the starter when the engine is running.)

I took the generator apart. It looked OK.

I tested the windings with an ohmmeter. Placing the test probes at each set of opposite strips of the commutator, I got low ohm readings, which means that the winding attached to a particular pair of strips is not open.

But why would I also get a low resistance reading if I touch the strips adjacent to an opposite strip? Or several strips away? Is this normal or is the whole armature fried?

I suppose I'll be taking the generator into a shop for testing. If it's fried, and costs much to fix, I'll be tempted to get a 6-volt alternator. Another mind game to play.

[dynaflash_8]

i think they make a 6 volt powergen.

[DLK]

The generator on my DeSoto hasn't been charging. Nothing on my amp gauge, and the battery was run halfway down. I tried the grounding-the-field trick and nothing.

(I suspect that the recent zapping of the system with 12 volts to start the car didn't help. I had mentioned in a previous post that DeSoto grounded the starter solenoid through the armature of the generator, to prevent engaging the starter when the engine is running.)

I took the generator apart. It looked OK.

I tested the windings with an ohmmeter. Placing the test probes at each set of opposite strips of the commutator, I got low ohm readings, which means that the winding attached to a particular pair of strips is not open.

But why would I also get a low resistance reading if I touch the strips adjacent to an opposite strip? Or several strips away? Is this normal or is the whole armature fried?

I suppose I'll be taking the generator into a shop for testing. If it's fried, and costs much to fix, I'll be tempted to get a 6-volt alternator. Another mind game to play.

Hopefully your generator problems are fixed faster than mine. Finally I took a 70 mile drive with my Dodge and it's reinstalled (for the third time) rebuilt 6v+ generator and it charged nicely from beginning to end.

[captden29]

don, i have jumped my 6v car so many times over the years with a 12v batt, never had a problem. the generator just gives up eventually but can be easily rebuilt by a competent shop for around $85. last one i had done was about 3 years ago for $75, still works great. i always put a new regulator on the same time as the newly rebuilt gen. goes on.a new belt does not hurt, and the battery should be tested to be sure it is good enough.once that is all done you are good for many years of service. don't forget to oil the generator at the two oil reservoirs. be sure to use a very light oil or it won't soak in well. capt den

[Tom Skinner]

Donald,

Have you checked if its Polarized correctly? Polarize the Generator with Jumper Wires at the Regulator? cut a wire (Short Scrap Jumper Wire)and jump between the Bat and Arm Contacts.

Firmly hold end of jumper wires to strike a flash between these terminals on your Voltage Regulator. This will Polarize your Generator to recognize a charge at the Ammeter - if this helps.

You may have inadvertantly un-polarized it, jumping or disconnecting stuff.

A Cheap Checks to save money. One more thing are the brushes in the Generator still good? Do they have any meat left to them or are they worn to a nub? Good Luck with your repair!

Tom

[DonaldSmith]

I'll do the flash thing. I downloaded Mr. Coatney's polarizing diagram - Autolite, therefore BAT to GEN. (Polarizing is not a bad word when it comes to our generators.)

In the meantime I noticed that the Armature post is bent. Maybe I didn't get a good connection. And I didn't use the usual star washer that I used everywhere else to get a good electrical connection.

Hmm... Could it be? The generator gets hot and the threaded post gets hot and expands, loosening the connection?

I'll fix the post, re-install the generator, with star washer, polarize the generator, and report back. After I sit back a while. To paraphrase Barney Phyfe, "Yep, I'll fix the post, reinstall the generator,..." repeated ad nauseum.

[DonaldSmith]

Generator report:

To straighten the Armature post, I determined that it was 1/4-28 thread. I happened to have a tap that size.

I drilled and tapped the end of a big, fat bolt, and threaded the bolt on the post as far as it would go by hand. Then I hammered the bolt a bit to staighten the post, threaded the bolt on more, and hammered it some more, until the post was straight and the nut would easily thread on all the way.

I scrounged up two star washers to each post, one to go between the fixed bottom nut and the wire connector, and one between the wire connector and the top nut.

i reinstalled the generator, and polarized it. Zap!

I started the car. The amp gauge snuck to the charge side. I turned on the headlights and the needle went negative. I revved the engine and the needle moved over again to the charge side.

The generator works! Thanks, guys, for the advice.

[greg g]

Try the grounding the field terminal to assure it will give you full charge. If you battery is fully charged and in good shape you genney shouldn;t have to do much work, but you want to know it can when it needs to.

[norrism1]

DaonaldSMith

quote: <I tested the windings with an ohmmeter. Placing the test probes at each set of opposite strips of the commutator, I got low ohm readings, which means that the winding attached to a particular pair of strips is not open.>

On gennys, set to Ohms then you hold one test lead to the shaft and with the other test lead you go to each contact to check for shorting. Any shorts are bad.

[DonaldSmith]

When I had the generator apart, it checked out OK. The brushes were good. There were no shorts to ground. I found out on line that the armature coils are all connected together, so no problem reading continuity between various strips of the commutator.

I think the real problem was the bent post. The nut could be really tight, without making a good, consistant connection. The more things heated up, the less reliable was the connection, witness the frequently dead starter circuit after an initial good crank.

Correction: The post is 1/4-28 thread, not 24.

All's well that ends well.

[Barabbas]

Hopefully your generator problems are fixed faster than mine. Finally I took a 70 mile drive with my Dodge and it's reinstalled (for the third time) rebuilt 6v+ generator and it charged nicely from beginning to end.

You Finally got it running! Congrats!