1951 8n charging question

[thompsonseatgrinder]

I'm having problems trying to get an 8n to charge. I am on my 3rd. new voltage regulator (Tisco). After installing the new VR, it will charge as it should for about 3 minutes and then the amp gauge will fluctuate on the charge side for awhile. The voltage will rise to about 7.2 and then the amp's (amp gauge)will drop back to "0". If I ground the regulator terminal, it will show charge again but only until then. If I shut the motor off and restart it won't charge until I ground the regulator terminal. This is a total restoration and everything is new on the charging system except the generator(which was gone over and is charging) Any thoughts? Thanks

 

[spokane 1]

yep the old 6 volt regulators need to be grounded. after install they also need to be polarized. "you may have forgotten this step" flashing the battery to the field just for a second.
Generator - How to Polarize at the Regulator - YouTube

 

[thompsonseatgrinder]

The regulator has a good ground and I did polarize the generator before I started the motor. Actually, the armature should be touched to the positive battery terminal to polarize. Thanks for the reply, Darrel.

 

[Soundguy]

yep the old 6 volt regulators need to be grounded. after install they also need to be polarized. "you may have forgotten this step" flashing the battery to the field just for a second.
Generator - How to Polarize at the Regulator - YouTube

very bad video to post. The person doing the video doesn't explain a circuit vs B circuit, though it is clear he is polarizing B circuit. ( even without knowing that the Lucas reg is B circuit ).

An 8n is A circuit.

 

[Soundguy]

The regulator has a good ground and I did polarize the generator before I started the motor. Actually, the armature should be touched to the positive battery terminal to polarize. Thanks for the reply, Darrel.

for the heck of it, motor test your generator to make sure it spins well. some times a genny with a partially faulted field will charge a little and motor a little, but fail a test of mor ethan a minute or so.

post back.

 

[thompsonseatgrinder]

I wanted to update on where I was at with this charging problem. Before I gave up on the 3 Tisco regulators and $100, I took the generator and 3 VR's to a generator repair shop. I didn't think the generator was the problem since it showed amperage every time I checked it. The generator shop said everything was working OK. The generator was putting out about 9-10 amps which confirmed my readings. All 3 VR's were good. I thought my next step would be to partially bench test the system using the tractor to spin the generator and use jumpers to tie in between with the VR on the bench. This worked great and charged as it should. The next step was to mount that VR on the tractor and tie it with jumpers and use the new dash amp meter. By doing this I would eliminate the new wiring harness installed and terminations checked several times. The generator was polarized by touching the arm and battery terminals as required by the "A" system. I had my analog meter on the battery. I also just for giggles, came off of the battery positive (ground) to the base of the VR. I did the motor test but I think the bench test proved it was OK. After all that it did not charge to my surprise. Thanks for the replies. What am I missing here? Any thoughts?

 

[Soundguy]

Motor and full field test will reveal all.

That Gen will charge with no regulator.

Tie arm to battery, ground field... Charge rate will be based on rpm.

High rom and full field and you can make 20-25a, shirt term before solder slings.

The reverse is motor test. Tractor off, belt off, arm to bat, should spin a little if bearing I good, should spin string with field grounded.

 

[thompsonseatgrinder]

I did the motor test and it ran OK. I had already put in new bearings and did a growler test then turned the commutator. The generator is working OK and the generator shop told me the same. I have ordered another VR ( fourth new one, 3 of them Tisco ) from NAPA ($86 ) and will try it later this morning. If this doesn't work, not sure what is next.

 

[Soundguy]

Vregs must have gotten real bad since I used a 'A' circuit one.

You can always wire the Gen for 'B' circuit and use a b-reg from a 53-64 gasser

But id find out what's failing in those a regs. Might just be bent contacts striking off square, and arcing in the small contact area.

 

[thompsonseatgrinder]

Well, I bought another new regulator from NAPA (Echlin) $90. Works like a charm. Who would have thought 3 new Tisco regulators and having a generator shop say they are working good would have caused this much time and trouble. I'm not saying they are all bad from them but I did get the 3 that were. Thanks to everyone for the input and I hope this will help someone else with the same problem. PS- I was lucky enough to return one of them to the local tractor sales.