The Stovebolt Site Forums The Shop Area The Electrical Bay Battery, alternator, voltage regulator or something else?

could be anything, for starters check all connections for cleanliness and tightness, if the fluctuation seen when running isn't caused by vibration of a poor connection, I'd think it's most likely the regulator, and you might be able to hear that clicking .... and figure out what the meter is actually saying, it's not reading hundreds of volts

Bill

Hi Bruce, which vehicle are you working on? A while back you had mentioned medical stuff going on, everything turn out ok?
Take Care, Don

Are you using a GM alternator with a single wire and internal regulator? If not, what alternator are you using?

It sounds like you've got the multimeter set on the wrong voltage scale. It needs to be on "DC Volts", indicated by a "V" with a dashed line under it. If the symbol is a V with a curved line under it like a lazy "S", you're on the AC volts scale and you'll get exactly the reading you describe, a randomly changing set of meaningless numbers. I like the old-style "analog" meters, the ones with a sweep needle, not a digital readout, for working on generator-equipped vehicles. Digital meters simply respond to voltage and current changes too quickly, and the old DC generators and vibrating-point regulators have a tremendous amount of fairly low-frequency voltage spikes that get a digital meter very confused!
Jerry

If it has an alternator, there would not be an external voltage regulator would it? Someone may have left an old regulator on it and bypassed it.
On the old tractors, I always use a one-wire GM alternator and strip out all the old wires and regulator and do a complete rewire. Fairly simple on old tractors, nothing to run except ignition and maybe lights.
NAPA has 12v coils with a built in resistor for the points.

It depends on which alternator was used for the conversion. First-generation alternators for both Ford and GM had external regulators. The 10-SI GM alternator was the first one to have an internal regulator, starting in the mid-1970's.
Jerry

Hummm, now that I think about it,,, the 67-68 Camaros had an alternator with an external regulator I think.

I believe that the first internal regulator for Chevrolet was 1973.

Just FYI: My 67 C20 has an alternator and an external regulator. You can tell them apart but it can be a pain in the #$%. Look for insulators on screws. They hold the regulator in place. Not on the posts that the wire goes to. Some alternators have enough vents in the back you can see the circuit board in there. And some do not. Part number is the best way and all of these ideas require that you pull it off and look at it. No short cuts that will keep you warm and dry come to mind.

external alternator regulator, 60's Delco style in my 58

Bill

The external regulator alternators are smaller in diameter than the 10-SI, and have a 2-wire square plug that inserts into the back of the housing. The internal regulated 10-SI has a flat rectangular 2-wire plug on the outer perimeter of the stator housing. There is an aftermarket regulator available for the early alternator that attaches to the back of the alternator, plugs into the square receptacle, and eliminates the need for an external regulator. I used several of those units while doing 12 volt conversions on farm equipment back in the early 80's.
Jerry

Thanks Hotrod Lincoln! That was the best description and the simplest I have ever seen. Even I can tell them apart now with just a flashlight. No matter how cold it is.

The external-regulator GM unit was known as a "Delcotron 1-D". I've tried to find some good pictures of each variety, but so far nothing wants to upload to my photo host site properly. Just search the following names:

Delcotron 1-D

Delcotron 10-SI

The differences are pretty obvious. The two blade terminals on the 10-SI are part of the internal regulator. There's a way to bypass the 10-SI regulator to see if the alternator or the regulator is responsible for a "no-charge" problem, but trying to describe the procedure without pictures or a video is sort of confusing.
Jerry

Working on getting all the gauges to read on my 41'. Is there a easy way to test output from the generator, and then, from the regulator to the gauge. Have easy access to both from under the hood and a good multimeter and amp meter.

Yes. Is everything hooked up properly? If so take a voltage reading at the battery then start & high idle the engine, you should read atleast 1 more volt. 2 or more is better right after a start. If the reading doesn't change or is lower it ain't chargeing.

If the engine has been sitting along time and/or the gen or reg has been disconnected or replaced, it may be necessary to polarize the gen. To polarize, momentarily touch positive voltage (via a jumper)to the gen's B(bat) or A(armature) terminal. They are the same terminal but different manufacturers label them differently. Take care not to touch the other F (field) terminal.
If the reg is hooked up to the gen, you can polarize at the reg terminals by momentarily shorting the gen's B term w/the gens A term.
Now test for chargeing.

You can test the gen easily for voltage output after you've polarized it. Disconnect both wires (to protect the reg) start & high idle the engine. Take a jumper and short the F (field)term to ground. Connect your VOM red lead to the gen's B or A term and the VOM's blk lead to gnd. You should read nearly double the gens rated output. i.e. on a 6v gen you should read 9 - 12 volts, 12v gen 16 - 24 volts.

Theres tests for the reg but make sure all connections are good and tight and corrosion free and all gnds are also tight.
Good luck
Dave

I had a similar problem on an International 350.
It sounds like your output voltage is jumping from 9.00 to 15.00 volts. Short version is that the belt was slipping. A couple of turns on the adjustable pulley and problem was fixed.
Hope this helps.