VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt '33 Generator question

I have a '33 207 in my fire truck that I just got up and running again. I had the starter and generator rebuilt at the start of the process. I also changed the truck from a positive ground to negative, including swapping the wires on the back of the amp meter and repolarizing the cut out.

Currently the amp meter shows a 10 amp charge with everything off, when the truck is running it pegs the meter on the charge side, adjusting the 3rd brush made no difference except when the brush was moved on the commutator there was some fluctuation on the gauge. The output to the battery when the engine is running is in the 9V range. My first thought was the gauge is bad but I'm not sure about that. When the battery is disconnected the gauge remains in the same spot.

I have talked with Chipper about this a couple of times and his suggestion was to run this by you all and see if you have any thoughts as to where I go next.

Any help is appreciated, thanks

I'm wondering if a ground or one item has gotten missed somewhere when it was converted. I'd start disconnecting everything beyond battery, generator, regulator and ignition after doublechecking the wiring on each one of these. I'm wondering about a missed switch, light or electrical accessory.

If it were mine I would draw a sketch of the schematic and sketch out every wire starting with the battery. Trace every wire and then draw it onto your diagram. Slow and steady and you will likely find something bizarre like a rotary switch, with one connection causing the problem.

Ok, I have looked into the schematic but will go over it again. Other than the light switch, headlights and tail lights there is nothing else electrical. No blower etc.

It can't be showing charge when the engine is not running. If something is drawing current it would show discharge. Try switching the ammeter wires to read discharge. When my engine is not running and the ignition switch is on the coil reads 6 amp discharge (if the distributor points are closed). If the relay points are stuck closed it may be draining back thru the generator. Try disconnecting the ignition coil wire and the generator wire and see if the meter moves.

What does the ammeter show when both wires are disconnected? If the needle is not centered and showing neither + nor - under that condition it is defective.

Then start connecting items one at a time and observe the needle.

Are you sure it was positive ground before you "Changed it over", the other scenerio is that the ammeter wasnt swapped until you did which would make it reversed connection now.
Tony

Thank you for the thoughts. Yes the truck was a positive ground and I swapped the wires on the gauge after that change so I do not believe that is it. I will disconnect the wires and see what happens with the gauge. I did disconnect the battery to see if it that made any difference in the reading but there was no change.

Based on that information my money is on a problem with the ammeter.

I recently had a similar experience with the ammeter in my '37 Master coupe. It happened on the last day of the Southern Fall Tour in October. It never read to the charge side. With everything disconnected the needle set halfway to the discharge side. It would read a greater discharge when I turned the headlights on. And the generator was working fine. I drove the car like this for about 4 months before I finally decide to practice being a contortionist to remove the instrument panel.

I carefully removed the ammeter from the instrument panel over the white paper on my work bench. This little hard black ball of something fell out if it and the needle immediately went to the neutral position.

Using a magnifying glass the best I could determine is that this was some type of a old dried up insect like an ant! Apparently that object had wedged near the needle pivot to restrict the movement. It was large enough that it would not fall out even when the needle went to full discharge.

I did some testing with the ammeter out of the car and it seemed to work fine. I reinstalled it and operation is back to normal.

If the ammeter is reading +10 amps with the battery disconnected, it is defective. You should start by replacing the ammeter and go from there..... You may be able to rezero the current one, but I've never had much success with that.

All the Best,

Chip

PS -- It was "Chip" (that would be me) rather than "Chipper" (the real expert) who "33Firetruck" talked with about this before posting. Maybe the real "Chipper" will have some thoughts too........

I believe I will start with the amp meter and go from there.

Sorry Chip! You would think with as many times as we have talked I would know better!

No problem at all -- we're frequently mistaken for each other. I'm the handsome one and he's the knowledgeable one.

All the Best,

Chip