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I have been chasing this rabbit for what seems like forever, and I need some advice from someone more adept in the wiring of these old trucks than it seems that I am. Situation: '50 model 3100, bone stock. Years ago, when I first started working on the truck, we stripped all the wiring out due to the fragile state that it was in. We bought a wiring harness from Chevy Duty, set up for generator application. Each wire is numbered on each end, and the harness package came with an instruction sheet for installation. We followed the instructions to the letter. Now---with a new hot 6 volt battery, a generator that will crank out in excess of 12 volts (I've checked it out),and a new voltage regulator, when the key is turned on, there shows a slight discharge on the ammeter. Turn the lights on, and a deeper discharge occurs. The discharge rate does not decrease with higher RPMs. I have checked and cleaned all the ground points hoping to correct the issue, to no avail. The VR has been polarized. I have checked and double-checked all the wires for correct position. BTW, this problem was not corrected with the new VR.

Now, here is where I'm scratching my head--per the harness instructions, a wire from the ammeter- terminal goes to the starter, and a wire from the ammeter + terminal goes to the VR Battery terminal, plus one to the horn. I have a copy of a reprint of the 1950-51 Wiring Diagram that, as I am interpreting it, sends battery power the the ammeter + terminal, connects the ammeter - terminal to the VR Battery terminal, and connects the horn to the ammeter + terminal. It seems to me that there is some contradiction between the two, unless I am not following the diagram correctly.

Any input from anyone that can help me clear this up will be greatly appreciated.

I think the ammeter is responding correctly. What is the voltage at the battery terminals at a high idle, with load and without load?

The wiring diagram from here shows battery + connected to ammeter +.

1. I don't think you polarize a VR?
2. Chevy Duty? I think is American Classic Trucks now?
3. See the VIO below.

The main feed wire from the starter goes to the pos. of the amp meter along with the horn. The neg. from the amp meter feeds to the ign. switch, Light switch & voltage reg. bat. term. & any other accessories.

George

When we get past Christmas, I will get back out to the shop and go through the suggestions and see if we can't get this sorted out. Thanks to all and a Merry Christmas to each and every one!

Same to you. See you next year.

well, we got through Christmas, had a great time with the son and his family (waaay too much gumbo for lunch) and got them on their way home. I decided to go out to the shop and do some testing. First off, the battery is good--no dead cell. Next, I went contortionist and went under the dash and checked the wires on the ammeter and ignition switch (which by the way is brand new)---all is as the factory schematic says it should be. Next, I checked the voltage at the battery terminals. Engine off, engine at idle and engine at high idle all come in at ~6.25 volts. That being said, I swapped the old VR back into the mix, polarized the gennie, and ended up with the same results. My guess is that I have a pair of VRs, both old and new that are bad. So, one new VR is on order to see if that is really the problem.

Put a jumper wire from the field term to ground & try it. This bypasses the regulator & should charge infinitely. Obvious don't run it long or fast like this as it can damage the gen.

Wrenchbender ...

Do the VR and generator have to be tuned (?) to each other? On the generators I've had rebuilt, my electrical shop always wants the VR that will be paired with it at the same time.

Thanks,
John

When I had the gennie rebuilt some time ago, I carried it to a very reputable electrical shop to have the work done. They did not say anything about pairing the gennie to a VR; at the time they were building and rebuilding both for individuals and also for resale through parts houses. My thinking is that pairing is not necessary, but I may be speaking above my pay grade.

When I rebuilt my generator (basically a cleanup and new brushes) I tested it per the shop manual. It basically consists of motoring the generator with a battery and an ammeter connected. I'll also run thru the adjustment procedure with the voltage regulator when I install it in the truck. Shouldn't be a need to "pair" the generator with a VR when rebuilding.

In the 1950s there was a trucking company in Nashville Tennessee that used my father's shop for all their electrical system maintenance. This was long before alternators were in general use, so those rigs ran very large Delco-Remy generators and 6-unit regulators that were about 6 inches square. Generators and regulators were rebuilt, paired up by serial number, and changed as a matched pair on a mileage and/or hourly basis. Dad rebuilt the generators and regulators and adjusted them to factory specifications on a Sun generator/regulator tester, and the company kept the paired units in inventory for specific trucks. Their maintenance supervisor said that charging system failures on the road were virtually nonexistent once that program was instituted.

Maybe "matching" components isn't necessary, but it's certainly effective.
Jerry

Kevin, what the manual says, and what you intend to do after rebuilding, can be called pairing by a lot of people.

Commentary:
"Pairing" can be defined as "adjust" the VR while a certain polarized gen is running or in static mode, using the ammeter or other meter, as I read the manual. Done after a rebuild/cleaning or new. On the other hand, the concept of interchangeable parts which was in full force way back, says parts off a shelf should work with each other. I don't think soldiers in the field or folks broken down, ever did anything but replace and drive. If the ammeter didn't act right, and they were mechanically inclined, consumers would adjust per manual or take it to a shop. Whether pairing is or is not the right word, the answer is: parts off a rebuild bench or off a store shelf will probably work OK. Usually rebuilt or new parts get some kind of "final test" procedure...or in the USA they did. Probably in China they do also....as demanded and batch checked by USA "global" companies. If a local shop, in business for a long time, wants to test parts together, it's a sign of a very good shop.

Most times the warranty can tell you how they feel about their parts.

Final report on this issue before we move on to some other issue---we got a new AC Delco VR from the friendly local parts supplier, got it installed, did the usual polarization of the GENERATOR, cranked the truck up and voila---the sucker charges like it is supposed to. I guess that I spent too much time "assuming" that the NEW VR was OK, when it is common knowledge that just because it came out of the box new doesn't mean that it will work as intended. As far a pairing the VR and gennie, that seems like it would be a good idea, just that in my 77 years, I have never encountered it.
BTW, this unit is as the other AC Delco VR was, stamped "Made in the USA" on the main frame. For what it's worth!

Thanks to all you who gave me input on this problem---maybe I can return the favor for some other poor soul wondering what the hey is wrong with his/her 'Bolt in the future.

Was the brand, Regitar?

Good work Jim. Your final reporting helps everybody already.

A foot stomp/lectern slap to what Bart said.

Otto, the unit I installed came in a box marked AC Delco. That may have been built by Regitar, I don't know. The only markings on the unit was the statement "made in the USA" embossed on the base by one of the mounting holes. That could indicate manufacture here, or Unknown Site Anywhere!