VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt '47 3600 charging system issues

I have a '47 3600 that I purchased several years ago disassembled and in storage for many years. I am nearing completion of a mostly stock restoration. I replaced the wiring harness, purchased a rebuilt 6v generator and a new voltage regulator.(Chevs of the 40's) The ammeter is original and has some movement but does not indicate much of a charge or discharge when running or starting. I probably have 6 or 8 hours of run time on the electrical system. I thought that I probably had a gauge issue since the electrical system didn't seem to show any other problems; battery stays charged, starter cranks over nicely, lights work. Then I noticed that the generator appears to be "throwing lead".

I spent some time going back over the 6 volt threads for the last 4-5 years. It appears that polarizing the generator is a commonly overlooked procedure but I remembered to do that. One discussion I reviewed indicated that it might be necessary to polarize the generator each time you disconnect the battery, especially if the vehicle sits for a long period. I haven't been doing that. I printed the service bulletin 1R-118 that someone provided (thank you) and read it. Based on the information in the service bulletin and several of the discussions, I probably shouldn't have assumed that the voltage regulator and generator were compatible even though they were the only ones listed for my vehicle and I purchased them from the same supplier.

Questions: Is my generator already "cooked" or is it possible it is still good? My multimeter has a max amperage capacity of 10A. If the generator is correct for '47 (and still works), it should be putting out 35A. Does putting a resistance into the system as described by the service bulletin drop the system amperage to 10A or less? I'd rather not fry my multimeter.

Any comments and suggestions are appreciated. Thank you.

Others around here will be better able to tell you by part number what you should have for the generator and regulator. I don't know the answer, but I agree figuring it out is the right first step.

The regulator should be a 3 terminal job, and contain a cutout, a voltage regulator, and a current regulator. The current regulator is what limits the current to 35 amps. The generator should not normally be putting out that much. That would only happen with a low battery or a bunch of accessories on or both. The 35 amps is a limit to keep the generator from doing more than that and hurting itself (it will try to do more if asked).

The cutout should be breaking the connection to the generator when it is not charging, either because it is spinning too slow or because the engine is not running.

The voltage regulator itself does most of the heavy lifting. When you start the engine with a low battery or a whole bunch of stuff on, the current regulator may take over for a short time to protect the generator, but as soon as the battery starts to come up the voltage regulator takes over. It will hold the voltage on the system to some particular setting as long as the engine is running above idle, and the generator is keeping up with the load. The service manual should tell you what the voltage setting should be, but it will be something very close to 7.5 volts. As the battery charges, the current, which has already fallen way below 35 amps, will continue to fall as the battery gets closer to fully charged.

On a normal daily used truck with a charged battery, you would probably never see it hit the 35 amp limit. You should see the ammeter go to "charge" right after you start the truck, and then drop as you keep driving, finally settling down to a point where it is charging just barely.

Hope this helps and sorry I did not answer your exact question. I don't remember exactly what is in 1R-118, but I will try to find it tonight.

To test the generator ground the field terminal. This should cause the generator to fully charge indicating the generator is ok.

^^Do what Chev Nut says to see if the generator is ok.

To answer your earlier question about service bulletin 1R-118, the resistance they put in was presumably to be able to set the voltage regulator while running a safe stable current (10 Amps), without any possibility of the current regulator coming into play. I would not use a multimeter that is limited to 10 amps if you wind up needing to do that. You will likely blow the multimeter fuse, and multimeter fuses are very expensive fuses.

http://www.ruiter.ca/mc/info/PDFs/1R-118.pdf

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Thanks for the helpful input. I won't be using the ammeter function of my 10A max multimeter since I have no way of knowing what current the generator will be producing, especially if it is malfunctioning. I will follow the procedures listed in 1R-118 and the '47 shop manual that involve voltage checks and adjustments.

The indication I have that the generator is throwing lead is a light spattering of lead on the inside of the band that covers the openings. Am I correct to believe that this overheating can be caused by either a malfunction in the generator causing an overcharge condition or a problem with the regulator causing an overcharge condition? If the regulator, then probably the cutout circuit; perhaps the points are stuck/sticking? Keep in mind that I have never seen the truck ammeter show much movement in either direction.

The truck is stored a couple of hundred miles away in northern Wisconsin. I am driving up there tomorrow for a few days. I will start to chase this problem down by checking the regulator cutout circuit (points clean, freedom of movement, air gap) using the shop manual and 1R-118 for guidance. I also will check, since the truck has been painted inside and out, that the regulator is properly grounded. There is a strong possibility that I may have shot myself in the foot by overlooking something simple. After making sure the battery is fully charged, I will reconnect the battery and polarize the generator (again). After engine start, I will check the generator voltage output and then put a jumper on the field coil points and check for a charge on the truck ammeter which is what, I believe, Gene is suggesting.

Any other thoughts, suggestions or warnings please let me know. I will let you know the results in a few days.

Larry

The lead is solder, of course, thrown by the armature getting hot enough to melt the solder where the wires attach to the commutator bars.
Yes, a stuck cutout could do it, with current flowing backward from the battery and through the commutator to ground.
Otherwise a stuck regulator contact putting full field current on full time will cause the generator to go to full output and stay there until something dies.
This situation can raise the voltage to high levels, burning out lights and ruining your battery.You should be able to verify that the battery and generator are connected to different sides of the ammeter.
If not, you won't see charge current.
This stuff isn't hard, once you understand it, but it's near impossible to learn by trial and error.
I suggest you get the best diagram you can and see if you can find a clear description of regulator operation.
You can't lose much solder without without opening the armature circuit, so it would be a good idea to take another generator when you go.
And take the original home, so it can be checked rebuilt before your next trip.
I have a lot of experience with this stuff, since I ran a ham radio setup in my '53 Chevy when I was a kid.
I tweaked the current limit up, to get extra charge, but it was too much and I ruined an armature.
The generator/regulator setup can actually give excellent service, but will never produce significant charge at idle.
Extended city driving at night can easily be a problem.
WL

I mentioned in the earlier posts that I have doubts about the truck ammeter. I turned on the lights with the engine off and the ammeter indicated a significant discharge, as expected. Starting the truck, however, does not register a discharge but does show a charge at increased RPM. That doesn't seem right; what I expect to see is a discharge during start and a charge after initial start with a tapering off of charge after battery current has been replenished. Engine off, I removed the regulator cover and installed an under dash type auxiliary ammeter ( Harbor Freight ) in series between the battery terminal and battery wire on the regulator. I realize it is 12v and not accurate for setting the regulator but my good multimeter is only good for up to 10A and I would at least be able to get some indication of what was happening beyond what I was seeing on the truck ammeter. About this time I noted that the cutout circuit points were heat discolored. I started the engine and noticed the cutout points arcing and the voltage regulator points open with the current regulator appearing to be closed. The ammeter I had wired in series was showing around 5 at idle and at a moderate RPM about 50. The generator output is supposed to be 35A. If the current is pushed through a 12v instrument by 6v does the instrument read half the actual value? When I checked the voltage at the battery terminal, it was about 8v at idle and slightly over 11volts when the engine was at moderate RPM. At this point, I decided to install the original regulator that I got with the truck to see what differences that might show. No more cutout point arcing but everything else was very similar. The shop manual had some "quick checks" listed among the procedures. Under conditions of high charge with a fully charged battery I saw the suggestion to disconnect the field wire from the regulator to determine whether or not the generator current output went to zero. It did not. Since it did not, the manual stated that either the generator has a grounded field circuit or the wiring harness was grounded. I will try to do a continuity check on the new wiring harness to make sure that is not the problem but my gut tells me it's the generator.

Comments?

A few points to ponder:

1) Regulator settings change with the cover off, so need to be checked with the cover on, at least for a final check. It wont cause it to be as far off as what you are seeing.

2) Amps are Amps, and it does not matter if an ammeter is made for a 12 volt car. If you saw 50 amps, you saw 50 amps. That is why the generator is overheating. You are definitely on the right track.

3) The starter current does not go through the ammeter. It is way to much and it would destroy the ammeter. It is normal not to see starter current.

4) The current regulator should have opened around 35 amps. Could it's points be stuck?

5) It is normal for generators to not charge much at idle. Other than that, your analysis of normal ammeter behavior is spot on.

6) Try disconnecting the field wire right at the generator. It's the smaller of the two.

Good luck and let us know how it goes. :)

Perhaps I misunderstand the how the regulator works, but I think the current regulator only functions when the voltage is too low for the voltage regulator (field circuit) to control the current output. So if the field circuit is grounded at the generator or in the harness, the voltage is uncontrolled and therefore the current is uncontrolled. At idle, the current is reasonable but climbs unchecked as the RPM increases.

I checked the harness for grounding and it seems to be fine. I removed the generator and brought it home with me. I am looking for a reliable repair shop in the local area.

The huge wire on the current winding is in series with the charging current, and that is the main thing that pulls it down. It probably controls the field, just like the voltage regulator does. If that's true, with your apparently shorted field, it would not be able to control the current. I imagine it opened and tried but the generator just kept charging.

You are correct that the current regulator doesn't do much in normal operation. That is by default though. A huge load like a half dead battery and a bunch of lights would probably cause it to operate, because the voltage would (probably) be held low and the voltage regulator would not do anything. When the voltage regulator is regulating, the battery is probably charged or somewhat close, and not enough current is being drawn to kick out the current regulator. Charged and almost charged batteries don't draw much current at the normal system voltage, so the voltage regulator is happily buzzing away not letting it get any higher.

If you disconnected the field, and it still charged, I believe you found the main problem. Let us know how it turns out.

Any recommendations for a generator shop in the Madison/Milwaukee area?

Charging systems are simple, if you have the magic, mysterious if you don't!
Even some shops are losing the magic, in these days of alternators.
I've never seen a shorted field, but can imagine it happening.
My first suspicion would be the terminal where the field connects to the outside world.
Check its insulation and the insulation on the wire that goes from it to the big field coil.
If that's all good, I suppose the field winding could have lost insulation somewhere and shorted to the case.
You can unscrew the pole pieces to check this, but it's gnarly stuff.
Unless you are a determined DIY type, the generator man may be your next acquaintance.
I know a couple of old timish shops, so ask around. Tractor people may know one.
You may have fried your new regulator, so it may be worthwhile to get another one.
Who knows, the original may be good.
Using the auxilliary ammeter is good, since you don't really know about the harness or its connections.
For what you'll do first, you don't really care about load currents, so just put the ammeter right after the generator, so it tells you, for sure, just what's happening.
It it reads discharge when the engine is idling, the cutout is stuck and you should get the fire extinguisher, or disconnect the generator.
WL