'35 VL Electrical/Generator Problem ?

[frichie68]

After each ride of 40-50 miles (with lights off) battery voltage drops about 0.2 volt.

Testing indicates charge rate is about 1 1/2 amp, lights off, 5 1/2 amps with lights on, 7 amps with brake light activated. Moving the 3rd brush to either extreme has no effect. Engine RPM has little effect-drops about a 1/2 amp or so at higher RPM.


According to the "Rider's Hand Book" the charging rate should be about the same (Amps) with lights on or off, should be a maximum of about 4 amps.


I replaced the generator brushes with new ones, very slight wear on the old brushes but all were shiny on the ends from contacting the armature. This had no effect on the charge rate.


Any thoughts or suggestions appreciated.

[1950Panhead]

Any thoughts or suggestions appreciated.

Your generator needs repair.
If you have original field coils and armature they probably have failed and need replacement.

[Steve Slocombe]

As the generator is still giving out power, I'd check the relay/regulator before tearing it down. The new solid state relays give a smoother current output than the original electro-mechanical make and break type.

[BoschZEV]

Testing indicates charge rate is about 1 1/2 amp, lights off, 5 1/2 amps with lights on, 7 amps with brake light activated. Moving the 3rd brush to either extreme has no effect. Engine RPM has little effect-drops about a 1/2 amp or so at higher RPM.

I'm a little confused by what you wrote. It sounds like you are mixing up charging and discharging. Also, to be clear, when you say it "drops about 1/2 amp" do you mean the ammeter registers a value that is 1/2 Amp less than it did at low rpm, or that the value is 1/2 Amp greater?

With the engine off and the lights on does the ammeter register 1 1/2 Amps, changing to 5 1/2 amps when you turn the lights on? If so, whichever direction the ammeter has moved from '0' for those measurements represents discharging. If you start the bike does the ammeter needle stay pointed in the same direction with little or no change?

[frichie68]

Thanks for the reply, electrics baffle me and I may very well be reading the meter wrong!
Engine OFF, lights ON, meter shows about (-)4 amps discharge. (Indicating I DON'T know how to operate the meter-and all previous readings were DIScharge, not charge.)

It's a new-to-me "Sears Range Doubler" meter, fairly extensive owner's manual that doesn't mention how to check amps at all.

The on-board amp meter on the bike is not of much use, incorrect 30 amp meter, barely moves to the discharge side when lights are turned on with engine off.

[frichie68]

Not being smart enough to operate the meter and measure amps, I went back to square one and measured volts:

Engine off 6.07 volts (a bit less than fully charged)
Fast idle/lights off 7.7 volts (bouncing between 7.2 & 8)

Fast idle/lights on very little difference.
Slow idle, a bit less but still more than engine off.

The generator is obviously doing something, maybe I don't have that much of a problem.
I have no idea how long/how far an old bike would go on battery alone. My main problem (?) is that I worry that a .02 volt loss after a 40-50 mile ride will leave me stranded some day with too little poop left in the battery for a restart.

[frichie68]

UPDATE:
Same (voltage) tests with analog meter:
Engine off 6 volts
Fast idle 5 1/2 volts
Fast idle lights on 5 volts

Indicates generator ain't doing diddlysquat.
I've heard that a digital meter will give false readings when testing a 3-brush generator, this is totally different.
Next step, figure out if it's the armature or the field coils-or both. Can't afford to buy a generator.

[BoschZEV]

Same (voltage) tests with analog meter:

It's a little tough to offer suggestions without more details. Where are you measuring the voltage? At the generator itself? At the voltage regulator? Across the battery terminals? Somewhere else?

[frichie68]

I checked the voltage directly off the battery terminals.
The earlier attempts to measure amps was between the (-)battery terminal and ground with the ground wire disconnected.

I did the tests for the field coils a while back when I put the new brushes in, but did not test the armature as I don't have access to a "growler". Is there any way to test an armature without a growler?

[BoschZEV]

Is there any way to test an armature without a growler?

You can only partially test an armature without a growler. You can individually test the resistance of the coils to see if any of them has developed an open circuit. However, a growler is required to determine if any have developed internal shorts. I have a higher tech instrument as well that uses the frequency dependence of the resistance to identify shorts without having to disassemble the generator, but if the generator is apart I always reach for the growler first.

[frichie68]

UPDATE!
Bench tested field coils and brush holders by the book and all seemed to be ok. Growlers seem to be non-existent, at least in my neighborhood, so no way to test the armature, I took the chance and ordered a new one.
With both armatures (old & new) on the bench, curiosity made me grab the meter and check for continuity around the commutators of both armatures. The new armature indicated continuity between every segment of the commutator. Not so with the old one, at least three of the segments had no continuity with anything. That was encouraging, they were "different", I'm thinking/hoping good vs bad.
I put the generator back together with the new armature and installed it in the bike . . . SUCCESS!
The (incorrect) 30 amp meter on the dashboard shows about 3-6 amps at fast idle, roughly the same with the lights on and increases appropriately with engine RPM.
I went for a 10 mile ride this afternoon, battery showed 6.03 volts before I started it up. Rechecked battery again after the ride, now showing 6.17 volts.
Thank you all for the help and encouragement!