The Stovebolt Site Forums The Shop Area The Electrical Bay High voltage with generator

I am having some issue with high voltage and I need to find out if there is an adjustment I can make at the regulator or is there some other problem going on. At idle, I am showing battery voltage, but as I increase the rpm, the voltage climbs as it is supposed to, but I got it as high as 19 volts before I quit. Who knows how high it would go with even more revolutions. The generator was rebuilt about a year ago, but I have done nothing with the regulator other than cleaning the contactors with a business card as recommended here, and I don’t know if the upper voltage limit is set at the generator or the regulator. Jerry, you probably know the answer.

Thanks, Lee.

You've probably got a set of stuck points at the voltage regulator, the coil behind the "F" wire in the regulator assembly. A wire shorted to ground between the generator "F" terminal and the regulator can also cause the problem you're having. Try disconnecting the "F" wire at the regulator and see if the problem goes away. You could also remove the regulator cover CAREFULLY and tap on the points behind the F terminal gently. If the voltage at fast idle settles down, burnish those points with a piece of clean business card or a slice cut from an index card. You can use 90% rubbing alcohol to clean the points, also.

DO NOT FILE, SAND OR USE OTHER ABRASIVES ON REGULATOR POINTS! If you can't clean 'em up with heavy duty paper, they're probably too pitted to save. Since regulator points vibrate several times a second, and they meet with a slight wiping action, sanding scratches simply increase the risk of sticking.

Changing the spring tension on the VR points regulates the upper voltage limit. More spring tension- - - -higher voltage. Remember that the setting will decrease slightly when the cover is replaced, so adjust the top voltage a tenth of a volt or two higher than you want it to be after the cover is replaced. Max voltage against a FULLY CHARGED battery should be 14.5-14.7 volts, measured at the battery posts.
Jerry

I pulled the regulator and cleaned the contacts again with some card stock; everything looks okay to my untrained eye. Nothing obvious anyway. I then turned the adjusting screw ccw, to loosen tension on the spring, one turn. Reinstalled and ran the engine at first with the field wire disconnected from the VR ( the field wire appears good with no shorts). At this point the voltage did not rise above about 14.5. Reconnected the field wire and the voltage was above 17 at a fast idle. I tried 2 more times turning the voltage down at the regulator with no change. Any suggestions as to what I can try next?

Lee.

You should not have gotten more than about 1 volt at the generator armature terminal with the field wire disconnected. Something, possibly internally in the generator, is allowing the field circuit to find a ground. Check the insulator at the "F" stud in the generator to see if it is contacting the housing. The only place you should get a ground for the field circuit is through the regulator points. I would consider 1/8 turn of the regulator adjusting screw to be a HUGE change.
Jerry

Jerry, I ran some of the tests you recommended and got mixed results. I did find that both terminals on the generator have a path to the housing. I guess that is bad, so I am going to contact the shop that did the overhaul and get it back to them. Thanks for all your help.

Lee.

No, that's actually normal. The Armature terminal will have virtually zero resistance when checked with an ammeter. The field terminal will have several ohms of resistance, since you're reading the resistance of the field coils, and eventually through the armature windings to ground. The only effective way to check a generator without a shop full of equipment is the "polarize- - - -residual voltage- - - -grounded field" check I described. Anything else requires specialized test equipment most hobbyists don't have unless they're named "Denny".
LOL!
Jerry

Who wants to bet against that Denny has a growler?

I'm pretty sure he does. I've also got one stashed away somewhere- - - -haven't used it in years! I think I've still got a slotting saw for undercutting armature mica insulators, as well!
Jerry