1948 Famall Cub with a 3 teminal regulator

The three terminal regulator on the Farmall Cub I am working on has: battery terminal, field terminal, and armature-gen-terminal. Wire from the battery terminal on the regulator goes to the amp gauge at the dash. I must have a short in the regulator or the generator . Amp meter shows a severe discharge when connecting to the battery terminal at the regulator. Wire makes sparks when connecting to the battery terminal. I am having the generator rebuilt and will install a new regulator. Would like to know how this system works. When running amp meter continues to show a severe discharge and volt meter at the battery shows no charge.

You have a cutout on your generater. Get the gen checked out. Then polarize the gen when installing and you probably will be good to go. Those cutouts were gereraly trouble free. Your service person should be able to check it out also. If you need to replace it make sure you get the correct regulator by using the Delco Remy # on the gen as your gen if original has the thired brush adjustable.

Based on the year and your description, I assume it is a cut-out system, no actual regulator. If the cut-out points inside the box are stuck shut, you will get your symptoms. A short inside the cut-out is less likely but could do it too.

I dont think you have a "short" in your genny, I think the cutout relay is stuck closed which is then a "short" TO THE GENNY which causes a high discharge when shes setting there not running, that dont necessarily mean the genny is bad however, as its near a short from its ARM to case frame anyway, see below:

If you get a severe high discharge current when you atatch the amp gauge wire to BAT on your cutout, that usually means YOUR CUTOUT RLEAY CONTATCS ARE STUCK CLOSED. In fact, if you were to remove the belt from the genny it would likely spin (motor) when that happens indicative of a stuck closed cutout relay. That dont necessaruly mean your gennys is bad, even a good genny does and should spin (with belt removed) if the cutout is closed when shes not running.

How it works is the cutout (a relay between BAT and GEN/ARM terminals) should be open when shes setting, but once the genny starts spinning and its voltage exceeds battery voltage, it closes so the genny can charge the battery buttttttttt when you shut tractor off it should open back up so the battery dont reverse discharge via the genny.

To see if non charging is the fault of your genny, versys a VR or other problem, run Par 5 of my Troubleshooting Procedure

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=665110

John T
John Ts Troubleshooting Procedure

Jim,

Thank you for the infomation.

Chris

John,

I took the generator off the tractor and put it in a vice. Hooked up the voltage regulator and installed an amp meter between the battern terminal on the regulator and the 6 volt battery. Grounded the 6 volt battery to the generator. I use a ryobi hammer drill with a cut off 3/8 extension and a 3/4 socket. Took the top off the regulator and the contacts on the coil inside the regulator were open. When I connected the battery teminal to the terminal on the regulator no sparks this time. I closed the points and the generator rotated counter clockwise which is opposite to what it should turn. Had the positive terminal on the battery connected to a ground screw on the generator. Generator would not charge while rotating with the ryobi hammer drill. I grounded the field and still no charge but the points on the regulator closed and there was a noticeable increase in esistance while turning the generator with the drill. I am taking the generator and voltage regulator to Acme electric in Seattle.

Gene,

Thank you for the information. I just took the generator and cut out to Acme Electric here in Seattle Washington. Their shop has been rebuilding starters and generators for things I've worked on for many years.

Thanks again,

Chris