The Stovebolt Site Forums The Shop Area The Electrical Bay 48 Chevy 3100 generator

I have a 6 volt system with a generator on my 48 Chevy 3100 and have noticed my cab ammeter gauge shows higher charging (halfway between the center and the charge side (right)) when I'm cruising on the highway. I have the 3.55 rear gears and like to cruise at 55-57 mph. Otherwise, when I'm just normally driving around town it stays in the middle of the gauge. I guess it's giving a good charge at high rpms.

Is this normal? Is this good for the battery and electrical system.
Thanks

I would check the voltage at the battery with the engine at the RPM which results in the ammeter showing the reading halfway between center and the charge side. If the voltage is not excessive at the battery, you should be fine.
Carl

At cruise RPM (2500 or so) the terminal voltage of a fully-charged 6 volt battery should be approximately 7.5 volts. The final check will be how often water needs to be added to the cells. Overcharging will cause rapid water loss, and voltage regulator adjustment below about 7.25 volts will result in a chronically under-charged battery.
Jerry

Thank you. I have an Optima red top enclosed battery. How do regulators go bad?

Mechanical regulators go bad in several ways.
The most common is the one of the small wires that activate the relays break after years of vibration. I have fixed a few of these usually they can be spliced and re-soldered.

The contacts that the relays activate can pit or wear. These can be replaced or burnished if they are not to bad off.

Worst is do to failure else where in the vehicle wiring the relay coil wire burns up. The whole relay coil has to be rewound.

Today most of these repairs are not done as it is cheaper to replace the regulator. BUt if you have to have an original regulator and a replacement is not to be found then repair can be done.

Relay coil. Where can I find it and how can I check it? Thank you

Please post the results of the voltage test I recommended. Unless/until that's done, we're wasting our time trying to advise you.

Using an analog (not digital) voltmeter will give you a more accurate reading, since trying to monitor the output of a vibrating-coil regulator with a digital meter sometimes results in an unintelligible bunch of gibberish on the digital readout.
Jerry

Hi Jerry. I'll have to do the check later in the week so please be patient with me. And I am guessing the relay coil is within the regulator. Mine is aftermarket so replacement is my easiest option. Thanks folks

The "relay coil" is actually called a cutout relay, directly behind the Bat terminal of the regulator. It's basically a magnetic on/off switch that connects/disconnects the battery and the generator to prevent discharging the battery when the engine shuts down. If the ammeter is showing any movement in the + direction with the engine running, the cutout is working. The points can get dirty, but that just reduces the amount of charge getting to the battery.

The control you probably need to be concerned with is the "voltage regulator" behind the FLD terminal of the regulator assembly. Increasing the spring tension on that set of points raises the voltage available to charge the battery. If those points get stuck or the field wire gets shorted to ground, the voltage will rise too high, resulting in an overcharged battery. Do the cruise-RPM voltage test before you start shotgunning parts at the job- - - -a simple cleaning and adjustment of the V/R points might be all that's needed. Don't use sandpaper or a file on the points- - - -they meet with a slight wiping action and sanding scratches can make them stick. A clean piece of a business card or an index card passed between the points should be sufficient to clean up any oxidation.
Jerry

Here's a '50, 6v generator on a 216 at 2500 rpm. Battery is a
Farm & Fleet I installed in Oct, 2008. Have never had a problem
with it starting Summer or Winter. Terminal voltage has
always stayed steady at approximately 7.2 vdc plus or minus
a couple of tenths. Have never had a battery charger or
maintenance charger on it even though I've thought about it
now that the battery is getting up in years.
http://www.pbase.com/dennygraham/image/160427600

Denny Graham

There are actually three relays total one is the cutout relay, one the current regulator and one the voltage regulator.

OK, if you say so- - - - -I started working on them in the early 1960's, but maybe the names have been changed since then.
Jerry

I never said the names were changed, but after 37 years as a electronics tech I know what a relay is. (example a windshield and a rear window are both glass, just function name is different)
The 1948 service manual identifies then by function name. But relays are the electrical device used to do the work. If one understands how a relay works by itself then that method of open and closing by magnetic action from electricity applied to the coil can be applied to what is going on.

As I had posted the links to the complete section of the manual that explains each part and what it provide to the charging circuit and how to test, clean and adjust for proper operation. Of course I am assuming that it is a 48 with stock electrical system we are talking about so the shop manual applies.

Oh, good grief- - - -another self-appointed "expert" with no practical shop experience! I give up!
Jerry

YEP NEVER REPAIRED OR BUILT A SINGLE CAR

Hi all. I'm back and will try all the things you have mentioned and will report the results. Again, thanks to all.

I connected my meter to the battery and it showed around 8. The face is small and not digital. So, I think I'm alright and need to put my brain in a 50s mode.

Thanks to all

If your battery allows you to check the electrolyte level, watch out for gassing and/or a drop in the liquid level in the cells. 8 volts will result in pretty rapid water loss. I'd be more comfortable with a maximum of 7.5 volts at fast idle against a fully-charged battery.
Jerry

Thanks Jerry. I have a sealed battery.

It does seem to take a lot of juice to start the truck then the generator recharges the battery.

I don't understand these 6 volt systems.

Thanks again

I charged up my battery and it starts great. Now I am looking at the generator and regulator. First the generator. Is there a way to put my meter on the output to check what is coming out? Again, I am running 6 volts. Then I'll move on to the regulator.
Thank you.

Here are some steps to take.
1. Check battery water and general battery condition to
see if it will take and hold a charge....Load testing
may be necessary.
2. Check wiring for damage and make sure all
connections at generator, regulator and battery are
tight and free of corrosion.
3. Make sure fan belt is tight enough to drive
generator at full capacity.
4. Run engine at medium speed. Using a wire, touch one
end to regulator base and other end to a good ground.
If this corrects trouble, regulator is not properly
grounded anymore.
5. If test 4 does not correct trouble, make this test.
Connect a wire from regulator terminal marked "ARM" or
"GEN" to regulator terminal marked "BAT" with engine
running at medium speed. If charging rate increases,
replace old regulator.
6. If test 5 does not correct trouble, make this test.
Connect a wire from "FLD" Terminal of regulator to a
good ground with engine running at medium speed. If
Charging rate increases, replace old regulator.

If none of the above test show a bad regulator then
there is probably a problem in the generator itself.

Hope this helps.
Ken

Thank you Ken.

Can this be done in a one man shop? Thanks again

sure but you may want another set of hands to help you out.

Here's a quick way to test the battery's cranking power. Without turning the ignition switch on, crank the engine for 15 seconds with a voltmeter attached directly to the battery posts (not the cable terminals). At the end of 15 seconds, while still cranking, the voltage should not be below 4.5 volts.

Turn the switch on, crank up the engine, and immediately go to a fast idle (1500-2000 RPM). The voltage should rise to 6.5 volts or more, and the dash ammeter should show at least 1/2 scale deflection toward the Charge or + side. Run the engine above idle speed for 10 minutes or more. The ammeter deflection should gradually diminish and the voltage should rise to 7.5 or so. If the system passes all these tests, you're good to go.

The most common cause of slow cranking and/or hard starting is loose and/or dirty cable connections or too-small cables. 6 volt systems need lots of current flow. #0 cables or larger with VERY clean connections and a good ground wire between the engine and the frame will go a long way toward quick starting and good cranking speed. There should be no more than 2/10 volt loss across any single cable connection, and NO voltage drop from one end of a cable to the other.
Jerry

Folks, I'm embarrassed but found the problem. I have been doing all your checks and tests, and they came out positive. So, I went back to the first step. I was grounding at the bell housing and when I moved the strap to the starter everything is good. In hindsight I would have looked at where this strap is located and not cleanliness or its condition.

I thank you folks for staying with me and providing all your pertinent suggestions.

Many thanks

Dennis, isn't it wonderful when a good plan comes together? Now go out and drive the wheels off it.

Thanks Martin. When's the onion burger festival?

Onion Burger Day is first weekend in May. Smalltown Weekend (Cruise) is first full weekend in June. Drive on over, burgers are on me.