Generator voltage problem

Tractor: 47 AV with magneto, 6v generator. Problem: With tractor running, charging voltage drops as you increase rpm. Battery is at 6.3 volts before starting, then after starting voltage drops to 5.85 or so, then continues downward as you increase rpm, 5.81, 5.79, 5.75 and so on. Back to idle it goes to 5.85. Ammeter is pegged to the discharge side.
Stuff I"ve done: Gone all through generator, with field grounded it puts out 9+ volts and increases to 18+ at rpm. So it seems generator is fine. New regulator, all new wiring, new ammeter. All generator and regulator mounts were ground down to bare metal to insure a good ground, test meter shows ground is good. Generator has been polarized more times than I can count. Jumper from BAT to A terminal on generator with fan belt off. Generator rotates a tiny bit clockwize. Will not polarize by jumping to the GEN post on regulator? I have tried more things, but I"ve gone on too long as it is. Hopefully someone has been down this road.

Do you have the positive terminal on the battery hooked to ground on the tractor? These tractors are wired positive ground. They will start & run with the battery hooked up backwards.

I had stripped & rewired my old H three times before I looked down & FINALLY noticed I had the battery hooked up backwards.

I can hear my Dad to this day.....
" ALWAYS Check the simple $#!@ (stuff) first !!"

No offense intended, been there..done that.

Where did you get the regulator and what is the # on the generator. They do list two regs for the Farmalls in that era. Maybe you should move the third brush a little closer this will make more amps. At least we know the gen is OK. If you ground the field what happens to voltage and amps what readings do you get with field grounded.

Thanks fellas, Positive terminal is the one that is grounded. Negative is connected to post on starter and also the one connected to the BAT terminal of the regulator,(but I'm going to walk out to the barn and double check, as your dad was right and these things always seem to boil down to something simple and stupid). With the Field grounded, ammeter is pegged on Discharge, volts are at 9+ at idle and climb as rpm is raised. Tisco regulator, 6v positive ground, 4 pole for a type A generator. Type B uses a 3 pole reg like on my "H".

Your suggestion made good sense, got me to wondering if I indeed had it backwards, so I went out and checked and it is correct, positive ground. I was half hoping you were right. Thanks

If it won't polarize by jumping the gen terminal on the regulator, there is an open in the wire from the reg to the gen. Wire is broken or terminals are not making contact.

Any chance the two wires are switched on the generator?

I will wade in!
There are no "B" type IH tractors that I am aware of. "B" generators are found on some Fords and other brands of charging systems. "B" generators have power from the regulator to the field, then to an internal ground in the gen. "A" type systems ground the field at the regulator, and get voltage from either the third brush, or the Arm terminal leading to the hot brush to make the field current.

My ideas may sound weird, but they are harmless.
With the battery charged, turn on the lights. (if it has none, connect up a head lamp or bulb from any headlamp, even 12volt, to some jumper wires.
with the tractor stopped, touch one headlight test light lead to ground, and the other to the Bat wire on the VR.
Watch the amp meter. If it goes positive, toward the charge side, you now know that the amp gauge is in backwards. If it discharges, it is in correctly. if it does not light, the wiring from the Bat terminal on the VR to the amp gauge, is broken. (not likely)
If it moves to the charge side, reverse the wires on the amp gauge.
If it moves to the discharge side, the amp gauge is reading correctly.
Assuming the gauge is correct, there is one check I need to have made, that is to place the volt meter on the battery terminals (needs to be an analog meter with a needle!!) and check the voltage there as it is started and run at differing RPMs. If the voltages are less then 6v, I suspect the regulator is not good.
If the F terminal is grounded, apply the same meter connections and give us the report at various engine speeds. A digital meter is great for new applications, but usually samples instantaneous voltages that give false true averages. Jim

Is you regulator made for positive ground it should say on the regulator. Those regs sold at that type of store have universal regs seems like some manufactures think one fits all they have never heard of pos ground and adjustable brushes. Thats why its important to know what your generators Delce Remy # is.

Jim,Owen,Gene; Thanks for your insite,I have followed up on each or your concerns. I have double checked the connections from the generator to the regulator, F to F and A to GEN. I have also replaced each wire, still the same result. Lights on, engine off, ammeter shows discharge as it should. Field grounded I get 9+v at idle, then a steady climb to 18+v at high rpm. Regulator connected, generator polarized, I get 5.85v at idle and a steady decline down to 5.55v at high rpm. I have tried 5 different regulators, including one new one, all provide the same result. Not to say they all could not be bad, even the new one. Is anyone aware of a way to test a regulator?

What kind of testing was done on the generator? When checking the generator for motoring make sure the field wire is disconnected or it may not spin. The generator should put out much more than 18 volts at high idle if the is no battery in the system and the field is grounded. Usually the voltage will rise until the armature shorts out. A armature may be shorted only while rotating. The faster it turns the greater the connection of the short as the windings move from centrifugal force.

The generator can be checked on the tractor by bypassing the regulator. Remove the wire from the F terminal on the generator. Start and idle the engine. Jumper the Bat and Gen terminals on the regulator. Check the voltage at the battery and the A terminal of the generator. They should be the same within a tenth or two. If not repair the wiring and connections. Do not overlook the grounding of all components. As you increase the engine speed the voltage should start to go up somewhere around 800 - 1000 rpms. With a good, fully charged battery you should see a maximum voltage in the range of 7.5 - 9 volts. If you have a generator with an adjustable third brush, the closer the moveable brush is set to the (A)rmature brush the higher the voltage will be. Those generators that have a non-adjustable third brush should be at the higher end of the voltage range.

Could the screw on the A terminal be shorting to ground when tightened?
Jim

You have a flying short in the armature of the generator.

Thanks Teddy, You are absolutley right! Finally an end to this. After trying everything I knew and some things gleaned from this forum, I decided to start over. I went through my pile of old generators and started by replacing the field coil twice, no difference. Then I tried an armature, it was nasty, but cleaned up ok. Walla, it worked. 9.5v at idle, 22+v at rpm with field grounded. With regulator, charges at 6.35 at idle and 6.85 at rpm. Ammeter shows cooresponding level of charging as well. Earlier I took all 5 of those old regulators I have and temporaily hooked them up to my "H" and all but one works. So the problem was a flying short and not the regulator. That explains why the armature tested ok on the bench growler, but not in rotation and why the problem got worse as rpm was increased. Thanks so much Teddy and everyone else who offered their ideas. Problem solved.