generator output

[Neshkoro]

I'm having some issue with the charging system on my A. The generator is stock. The cutout kicks in when the car is started. The ammeter reads zero. I've tried another ammeter and it reads the same. i measured the amp output and the voltage output at the generator with my digital multimeter. Both the amp and volt readings are unstable. The numbers bounce around so much I can't get a steady reading. I was thinking of just replacing the generator with a 6 volt positive ground alternator.
Ant thoughts on the generator?

[Badpuppy]

Check voltage with a DMM at the battery terminals, it should be stable there. Maybe also at the starter post. Instability is caused by the ignition coil spikes. The DMM only samples voltage, at about 1 Khz.

[Bob C]

Use an analog meter, the digital do not like the A's electrical system.

[Will N]

Try moving the third brush up to increase the generator output.

[AL in NY]

If you haven't driven your car in a while, the generator may need polarizing. To polarize, loosen the fan belt and then take a heavy gauge wire and jumper from the starter switch to the generator side of the cut out. Do this for about 3 seconds, the generator should spin like a motor.

[ndnchf]

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There is no need for a heavy gauge wire to polarize. It is only carrying a few amps to the fields. After loosening the belt, just use a simple jumper wire from one cutout terminal to the other cutout terminal (bypassing the cutout). A second or two is all it takes. The armature should turn like a motor.

Here is a video in how to do it off the car.

https://youtu.be/cvTico_p6K0?si=Kf0grq6K7bMrDcW4

Here is a video about adjusting the third brush.

https://youtu.be/PL94VX3GIq8?si=Q2KiN7m6rURleGWV

If you are still having problems, send me a PM. I can repair or rebuild it for you.

Steve

[nkaminar]

There are a number of possible reasons for a jittery output. One is the meter. Like others have said, try an analog one. The commutator could be dirty. Take the rear cover off an see if it is not bright shinny copper. The brushes could be bad or not making complete contact. Make sure the brushes are moving in their holders and they are not worn to the point of not being able to make contact. The other reason is a short of open circuit in the armature. You will have to take the generator apart and put the armature on a growler to test it. The cutout could be bad. To test it, at a fast idle, bypass the cutout to see if the voltage and amperage output comes up.

Or, it could be bad connections to the battery or the battery ground. Any connection along the path to the battery should be checked for bright metal and tightness.

If you intend to do a lot of driving and don't intend to enter 100 point judging, an alternator is a nice upgrade.

[Neshkoro]

Thanks for the advise! I'll do some testing next week and let you know what I find.
Thanks.

[Marshall V. Daut]

"Try moving the third brush up to increase the generator output."

Actually, to increase the generator charging rate, you move the third brush DOWN towards the ground (in the direction the crankshaft and hence generator pulley turn). To decrease the charging rate, move the brush up towards the hood. Remember:
Charge UP, brush DOWN;
Charge DOWN, brush UP.

Marshall

[Will N]

Originally Posted by Marshall V. Daut

"Try moving the third brush up to increase the generator output."

Actually, to increase the generator charging rate, you move the third brush DOWN towards the ground (in the direction the crankshaft and hence generator pulley turn). To decrease the charging rate, move the brush up towards the hood. Remember:
Charge UP, brush DOWN;
Charge DOWN, brush UP.

Marshall

Oops, than Marshall!

[Fullraceflathead]

When taking your voltage readings at the battery terminals when the engines at an idle you should not see any output until just above an idle when the cutout actually closes.

[Neshkoro]

Here is an update on the generator. I did measure the voltage at the battery. Car not running, 6.0 volts. Car running, 7.5 volts! The ammeter in the dash was still reading zero.
I disconnected the battery cable while the car was running and put an ammeter in line between the cable and the battery post. It read about 7-8 amps!! Its a -30-0+30 ammeter. Can't get an accurate reading at such a low amperage! Go figure! Turns out, for whatever reason, the ammeter on the dash does not shown a reading. I then, temporarily, put the other ammeter in place of the one in the dash and it reads about the same as when it was at the battery. So, after all that monkeying around the problem was the ammeter! I would have thought if it was not reading anything, it would be open (no current passing through), and the car would not start or run. The ammeter must be shorted out. I'm going to order another ammeter.
Thanks for all your help and advise. As simple as these cars are, I'm always learning!
Thanks again!

[Fullraceflathead]

Glad to see you figured it out!!!

[AL in NY]

I had the same ammeter problem, wouldn't read positive. Didn't monkey around with whose cheap vendor ammeters, bought one from westach. Expensive, be now I KNOW it's going to work for a long time.

[rotorwrench]

None of the repros are made to function as well as the old OEM ones.

A person can test one with a low battery and a battery charger with correct voltage. Connect the amp meter in between the charger and the battery to read either a charge or discharge depending on polarity of the connection. It should read close to the amp meter on the charger if a person still has an older charger that has an amp meter on it.

If the internals melt or get crusty then the meter is toast. If the little magnet loses it's gauss then the meter will not go back to the zero position. If the needle dislodges from it's support then it won't read at all or at least not correctly. They all wear out eventually.