The Stovebolt Site Forums The Shop Area The Electrical Bay Still looking for an answer.

Still trying to get an answer. If I can get the generator to turn with power supplied to the ARM terminal and grounded, does this mean the generator will supply voltage to charge a battery or does it just mean the generator will turn but not necessarily charge. Thanks

I thought the charge was based upon the rpm of the vehicle but.


here is some stuff that might help you

I use that test and if it motors it should function as a generator.

Hy Bart_Bosco, what truckernix said.

here is some stuff that might help you [/quote]

This referance is a very good overview of how generators work. This should be a standard referance to be used for all of the "my generator (or battery),,,) type questions.

Dan Bentler

If you wire the generator as a motor, it should turn and draw 5 amps on the bench with no load. I do not recall where I read that, but I do recall performing that test to verify that my generator was operating correctly.

Thanks for your help. I took this generator apart and cleaned the commutator where the brushes meet it, made sure the brushes were in good shape and put it all back together. I will reinstall it and see what happens. It would run like a motor when I tried it on the truck but would not generate voltage even with the Field grounded. After reading the post explaining how a generator works I may have figured a problem. I may try new brushes as when it did charge the rate dropped quite a bit at highway speed. Maybe my brushes are to short and do not have enough pressure against the commutator. Thanks again

I did that once and forgot to install the fan belt on nice and snug and took me awhile to realized why it wasnt getting a good charge,

Today I took apart the generator and cleaned it all, bench tested it with a battery and it turned just fine, re-installed it, polarized it again and took a voltage test from ground to the ARM terminal right on the generator with the engine running well above idle. Still no voltage.
Is it time for a new generator?

or alternator

What engine rpm are you running while testing for charge?

Did you do the test without the harness connected to te generator?

Bart: If you got the genny to run like a motor then you have a good armature, and good brushes. Time to look at field coils and a regulator. Just to keep it honest check the pulley to the shaft. Should be nice and tight. Make sure the belt is not all the way down in the groove. Some belts are too narrow and wont turn under load if they are bottomed out. Follow the wire diagram to make sure you have the right connections. Autozone has a regulator but it is expensive. $82. Might try NAPA for a comparison.

I made sure the belt was tight, has the correct pulley, all connections are good, the wire harness is brand new and tested those connections, had my wife rev up the engine when testing voltage. All this done I still had no voltage at the ALT terminal. The regulator could be bad but I still would have voltage coming out of the generator and do not. I am going to say bad field. I ordered a new regulator from Napa and am getting the gen rebuilt or purchase a rebuilt one from Jim Carter and be done with this. When I started this truck a few years back I would spend days trying to figure out how to save $200 bucks. Now that the truck is done the $200 seems like peanuts, but the truck is really nice.

well at least you are a winner on this site,
we charge you nothing for our suggestions, be they good or bad

how about a pix of your truck

I get an error in your photo bucket..
might be one to sign in on, dont know...

Here is why I asked if the wires were disconnected from the generator for the tests. Have a look at the third entry by tomctomc. generator test

Here is my "48" 3100

nice, I like the color, now get it charged up

What about your regulator?

I ordered a rebuilt generator and installed it tonight. Charges like crazy now. I also installed a new regulator just to eliminate future problems. I found out one thing, an alternator that motors does not mean it will charge. I read more than once in my research on this charging problem that if a generator will motor it is good, not true!

Remember what was said about "field coils" in the genny? That is what is wrong with your old gen. The permanent magnets the field coils are wound onto are what makes the low voltage needed to get a signal to the regulator. Current from the regulator to those field coils increases the magnetic field strength and increases the gennys' out put. If the field coils are bad, no change in field strength and no more current out of the genny. Genny will motor with bad field coils. It won't motor with a bad armature or bad brushes, or a bad commutator. Field coils are hard to test. Little resistance in a coil of wire. So for future ref check the volts at the field connection. You should see the working volts need to boost the out put. If the field coil is shorted, common. The volts will be low.

Still having a problem. The ammeter showed a charge and after some run time came back to center. I drove the truck 10 to 15 miles and had to turn the lights on. Meter showed a discharge all the way home and the dash light dimmed. Parked the truck and came back an hour later, started it and gen is charging again. I checked battery voltage with truck not running, it was 12.5volts. I noticed driving home that every once in a while the ammeter would jump to charge and then back to discharge. I am wondering if I have a ground problem. Checked every place I could think and found nothing. I have all new wires and a new regulator. Could something be getting hot and causing problems?

You need 3 things
1. Training.
2. A good volt ohm meter
3. A good ammeter connected in series with the generator.

might be a sticky relay in the regulator, or a loose connection on/in the generator or regulator - did you polarize the gen when you re-installed it and regulator?

Bill

I did polorize the generator when I installed it but I know nothng about polorizing the regulator. It charges fine now after the truck sat for an hour. I guess I will need to get out the service manual and just figure this out. I have a good volt meter that I use for work but it only has a clamp on amp meter. I will have to get one that can connect inline.

"I did polorize the generator when I installed it but I know nothng about polorizing the regulator."

How did you polarize the generator?
The polarization is done at the voltage regulator.

Did you place a jumper between the GEN and BAT terminals on the voltage regulator? Done with the battery, generator, and voltage regulator in place and wired up; and, the ignition off.

leitmotif,tclederman and red58 have given good advice. Use an "Amp" meter rated over 40 amps and hook it in line with the Armature Connector on the genny. Start the truck and see what current you are drawing. Turn on items like headlights one at a time When all including the heater motor and wipers are on you should have less than 40 amps. If you have more you need to determine which one is pulling the most. If the regulator is working a volt meter at the battery will read 14.5 volts DC when it is charging. Do this at a fast idle so that the genny can do it's work. One thing at a time will let you know what is going on with each load that you have. I have seen heater motors that run but draw so much current that they will drain the system rather quickly. Wiper motors can draw a lot as well. Halogen head lights can pull too much as well. A bad coil or no ballast resistor will use a lot of current. So do this 1 item at a time. And let us know what you find.

I did polarize from the GEN to the BATT terminal and held it for about a second, twice. All of this makes sense but none of these tests would make a difference if I am not showing a charge with no lights, fans or other accessories turned on. It showed a charge until I had drove the truck about 15 miles and then quit. I am going to run a ground to the frame and see what that does first and then check voltage to the battery at high idle. I will keep progress posted.
Thanks

I am beginning to think everything is working fine. If the battery is charged and the lights are on the ammeter will show a discharge until the regulator kicks back in which will not happen until the battery voltage drops. This charge may be hardly noticeable on the ammeter gauge. I am going to put some miles on during the day with the lights on to see what the battery does. If it is acting up I can just turn the lights off and get home. If the battery stays charged I am going on about nothing.

once the battery is recharged after starting, the ammeter shouldn't show a discharge except for a second when something like the headlites are first turned on, when running the generator is supplying all power required, not the battery ... OTOH, the ammeters aren't precision instruments, when the system is actually 'neutral', no charge going to [or from] the battery, the ammeter may appear to show a slight discharge, or charge - you need to learn what's normal for your gauge

Bill