The Stovebolt Site Forums The Shop Area The Electrical Bay Voltage Regulator Adjustments

I have a 1950 GMC 1/2 ton (6 volt positive ground) that I am trying to adjust the voltage regulator on, and need a little guidance. I recently had the generator rebuilt and tested, and everything is within spec on that. Now I am trying to get all the settings within spec on my voltage regulator.

I do have a shop manual for the truck, and the procedures seem pretty simple. I have made all the correct mechanical adjustments (point gap, air gap), and now need to make the electrical adjustments. The manual doesn't mention in which order I should make the adjustment in, as far as adjust cut out relay first, or voltage regulator first, or the current regulator first. Does it matter in which order I adjust the three? Will adjusting one effect the others? The reason I ask is I could not get my cut out relay to open and close within spec. The previous owner was running an 8 volt battery, and my thinking of why I couldn't get cut out relay adjusted was because the voltage output was cranked up because of the 8 volt battery. It seems to me that I would need to get the voltage output within spec before I could adjust the cut out relay. Is this correct?

As mentioned the previous owner of the truck was running an 8 volt battery, and I suspect that the voltage output was turned up because of this. My manual says to adjust the voltage output by using either a fixed .75 ohm resistor, or .25 ohm variable resistor. I can't seem to find a .75 fixed anywhere. Does anyone have a part number they could point me to? I was able to find a .80 ohm fixed, would that be close enough for adjustment purposes?

Any help in finding the .75 ohm resistor, or tips for adjustments would be greatly appreciated.

Thanks in advance,
Jake

Jake - I am really interested hearing whatever advice you end up getting. I'm not sure exactly where to start to try to help you...

Are you still running an 8 volt battery? What is the voltage regulator you have(6v? 12v?)?

Do you have clean & proper size (minimum 2 ga) battery cables?

What problems were you experiencing to lead you to want to adjust the voltage regulator, or is this an initial setup?

Brad

Edit: Here's a 1950 Delco manual

This might work:

http://www.autozone.com/autozone/ac...-ballast-resistor-with-threaded-terminal

Adjustable if needed

I am not running the 8 volt battery. I have got a brand new optima 6 volt, and trying to get everything back to original specs. I do have all the correct 00 cables and grounds. The generator is charging the battery, and the voltage regulator is working, I just want to make sure it's adjusted properly before I fry the freshly rebuilt generator.

The voltage regulator and generator are correctly paired together. I think the previous owner had cranked the voltage output up on the regulator to charge the 8 volt battery. When adjusting my cut out relay, I had to turn the adjusting screw a lot to get the points to open. When the points finally did open, the voltage jumped from 7 volts, all the way up to 12-13 volts. So I am guessing I need to get the voltage output properly adjusted before I can dial in the cut out relay. And according to the manual I can't adjust the voltage output without the .75 fixed resistor (or .25 variable). I have found a .80 resistor online, I am hoping that will be close enough to make the adjustments I need.

Like I said the manual procedures seem pretty simple, just want to make sure I am doing things in the correct order. I welcome any tips or tricks to dial these in.

Thanks in advance,
Jake

The only purpose for the resistor is to simulate a fully-charged battery to do the final voltage setting. The simple substitute is- - - -surprise- - - -a fully-charged battery! As the internal resistance of the battery increases, the generator output tries to rise to continue putting current into the battery. The 1/4 ohm resistor in series with the charge current drops the current sufficiently to get an accurate adjustment of the voltage. I use a 6 volt sealed beam headlight with both high and low beams wired in parallel to simulate the resistor, and wire it between the BAT terminal and the ammeter to do a final adjustment. BTW, I started servicing DC generator charging systems in the early 1960's so this is actual experience talking, not a quotation from a service manual.

Starting out- - - -adjust the closing voltage. With the engine idling VERY slowly, like 400 RPM or so, the cutout relay points should be open, and the voltage at the armature will be below 6 volts. S-l-o-w-l-y raise the RPM and watch the voltage. The cutout should close at about 6.5 volts or slightly above. If the regulator has been adjusted properly for the 8 volt battery, the closing voltage will probably be 8.5 volts or so. Drop the spring tension on the cutout points to get the 6.5 volt setting. Don't go below 6 volts, for reasons I'll cover shortly. The next setting is the current relay, the coil behind the Armature wire. Put a heavy load on the electrical system such as high beam headlights, heater blower, brake lights, radio, and anything else you can turn on. The idea is to make the generator produce maximum current. Adjust the current regulator to 30-35 amps with the engine at a fast idle, 1500 RPM or more. Shut down the "load" circuits and proceed to the voltage regulator setting. Final adjustment- - - -attach the inline resistor (headlight) between the battery wire and the BAT terminal on the regulator, fast idle again, and adjust the voltage regulator coil (behind the field wire) to 7.5 volts. Be aware that putting the cover on the regulator will lower all the settings slightly, so carefully check all your settings by placing the cover on the regulator after each adjustment. To get an accurate measurement, cycle the current and voltage regulator points several times by pushing the points open and allowing the cutout relay to cycle. Be careful not to short anything out while removing and replacing the cover during the adjustment procedure!

Final test- - - -drop the RPM back to the S-l-o-w speed, and be sure the cutout relay opens every time the armature voltage drops below 6 volts. If it doesn't, the battery reverse current will make the points stick, and the battery will discharge itself through the generator. Good luck!
Jerry

Or buy an alternator and take the heat from the stringent purists.

Jerry, thanks so much for the info!! That was exactly what I was looking for. I was hoping to get some guidance from someone with experience, rather then another link to a Delco manual.

I just have a few more quick questions. I am doing a frame off resto, so I do not have any other curcuits hooked up. No lights, radio, nothing. Just basic wires to run the motor. Should I wait to adjust the current output until I get some of that hooked up to create a "load," or is there some other way to simulate the load? I have all my electrical stuff in storage right now, I would have to dig it all out to hook it all up, so if there is another way to do it that may be the way to go.

As far as the resistor, I am guessing that I do not need it to adjust the voltage output. It is a brand new optima battery that has only run the motor for about 20 mins total. However, if you really do recommend that I use the head lights as a resistor, I will go dig those out of the storage unit.

Thanks again for the info, and I will try and get this thing adjusted in the next few days!

Jake

1.5 ohm resistors are common. You could put two in parallel to get .75 ohms, but I like Hotrod's ideas better. You already have the battery and headlights.

Finding resistors that can survive the wattage necessary to carry charging current is difficult. I used to make my own 1/4 ohm resistors for training purposed by purchasing four 1 ohm 100 WATT resistors, and wiring them in parallel with each other and connecting #6 wire test leads with heavy alligator clips to both ends of the resistor stack. Smaller wattage resistors will simply burn out in about 5 seconds. A 100 watt wire-wound resistor is about the diameter of a big ballpoint pen, and about 2 inches long, made of ceramic material with a piece of nickel-chrome wire wrapped around it. It is not something your local Radio Shack is going to have on the shelf. I had to special-order mine.

Yes, both current and voltage output needs to be adjusted. A Snap-On carbon-pile battery load tester is what I use to put enough load on the battery to get a good current regulator adjustment. Mine cost a little over $1,000.00. I gave you the shade tree method of approximating the tester load. Another method of getting the current regulator to max out is to put an almost totally-discharged battery in the vehicle, boost-starting with a second battery, and quickly raising the RPM. The generator will go to maximum current regulator output trying to charge the dead battery. You'll have 2-3 minutes of time to make the current adjustment before the battery begins to develop a surface charge and starts giving a false max current reading.
Jerry