losing my mind, generator

Woodie1

Woodie1

Well-known member
Went for tour yesterday & found the ammeter wasn't showing a charge. I have a diode converted cutout on it. The cutout tested good. I couldn't find any issue with the generator internally. This morning I put a spare generator on & it was showing about 7 amps at a fast idle. Tjought all was good. Changed oil & when I started the car up to circulate the oil, I saw no charge on the ammeter again. I changed out the wire harness from the cutout to the terminal box & still no charge.I don't know what I'm missing. I though I had it solved with the different generator.Moving the 3rd brush does nothing. Horn honks god in garage & light on shows discharge. Our car has always showed a charge on the meter when driving. Changing the ammeter doesn't help either.
 
With the engine at a fast idle, measure the voltage on the generator side of the cutout. If no voltage then the generator is bad. If there is voltage there then measure it on the cutout side. If not there then the cutout is bad. If there is voltage there then there is an open circuit somewhere down stream. If you have the fuse that mounts on the starter that may be bad or the fuse holder may be bad. Another place to look is the ammeter and any connections all the way to the battery.
 
Could be cutout has gone bad. Unlikely the diode itself, but its connections to the outside. Can measure good with an ohmmeter but opens up with higher current. Open cutout can destroy the generator rather quickly.

Bridge across the cutout to check.
 
The head ache continues. I gen #2 apart this morning (the one that gave me a 7 amp charge at one time) & found a couple of cracked wires. I replaced them & put the #2 gen back on car. Behold it showed 7 amp charge again. I shut the car off, did something (don't remember what) & started the car again, no charge on the meter again. I checked the voltage on both sides of the cutout with both gens (each has a converted cutout) & was getting less than 1 volt at fast idle on the armature side & about 6.2 volts on the battery side. With gen #2 I moved the 3rd brush from min to max positions & still did not get amps on the gauge.
 
Don't forget to test the ground side as well-it's equally important. Your testing so far says the gens are not doing their job so if ground side is all good the generators need a closer look. As stated,nkaminar's test sequence is the way to go.
 
If I start having intermittent issues with the electrical system, I'll check all of the electrical connections for loose terminals and signs of wire damage. The diode can be tested with an Ohm meter or a load off of a battery. It will only pass current in one direction but no passage in the other direction. The generator should be tested. Field coils should have a specific resistance when tested with a Ohm meter. Both the field and the armature can develop heat related problems if the winding wires have cracks or shorts. The armature would need a growler to test it. The output terminal needs to be checked for deterioration of its insulator through the case. The field is the third brush circuit so all related connections have to be good.
 
As stated in Post #11, the ground on the generator could be bad. Unlikely but possible. Run a wire from the generator to a good ground. You can use the screws that hold the cutout. If the measured generator is still 1 volt or anything less than 6 volts, then the generator is bad.

You can also just place the ground side of the multimeter on the generator housing when you measure the output voltage. If you get a good voltage that way then you have a bad ground. Scratch the housing with the ground probe so that you get a good contact.

As the Master said, if the fuse is bad then the engine should not run. Unless the car is wired funny. You stated earlier that the head lights work with the engine off, so that would indicate that the fuse is good, if there is one. I am betting both generators are bad.
 
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Generator #1 had a new armature put in this summer & the field windings were replaced some time not too long ago. Gen #2 is aging internally but both Gens worked this summer. It seems odd to me that gen #2 would show a charge & then not show a charge.
 
Electrical components can give out for a several reasons. It doesn't always make sense on what's going on until inspection and testing finds the problem. Shorts or loose connections are the most common problem but diodes can blow out. Worn bearings in the Gen can cause rubbing of the armature which generates heat. The brushes or there springs can wear out and fail.

I once had a short on my panel light in my 29. It melted the ammeter and fried the associated wires in there pretty quick. I put a fuse at the starter location after that but the generator also took a hit.
 
I returned to the two problem generators & now have them working. On one of them I had out the 2 wires that connect to the brushes on the wrong brush holders. On the other generator I did find a broken wire coming from one of the field coils. This one was harder to detect as it was come & go. I feel better now.
 
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