Packard Forum Index » Pre-War (1899-1942)

Hi everyone, I've been a reader for a while, and decided it's time to join. I have a 1936 120B Sedan, and recently i had to replace the regulator. Apparently the generator was good, but nothing was coming out of the regulator. This made sense as every few weeks I'd have to recharge the battery. I'm not the best at electrical stuff, especially on this car, so I wanted to come to the experts.

The voltages I'm seeing off the battery and reg seem odd. It is an Autolite 6V positive ground system. Battery is an Optima. Here's what I'm seeing:

Battery with power off: 6.2V
Battery with Car running, positive meter lead on positive terminal: approx 10.5v (this was consistent through all tests)
Battery with car running, negative meter lead on positive terminal: -2.0v
Battery with car running, negative meter lead on positive terminal, headlights on: -5.0v

Regulator wire with positive meter lead on ground: jumping all over (same with lights on or off)
Regulator wire with positive meter lead on the wire, headlights off: .03
Regulator wire with positive meter lead on the wire, headlights on: -.5

I don't know if I need to repolarize, or if that has anything to do with the numbers, but everything I'm ready says these are way too high.

The 5a fuse in the regulator is not blowing either.

Any thoughts?

Have you checked the battery to see if it is good? The charging voltage should not be 10 volts. You should be seeing a charging rate more around 6.8 or so. Check all your grounds make sure the regulator is grounded and make sure all other connections are clean and tight.

Afraid I am not astute enough to fathom your tests other than you are seeing way too much voltage across the battery.

Optimas HATE being overcharged. Ideally you would see 7.2 volts across its terminals with the engine running at a high idle.

Agree you should check the grounding of the gen and reg; running an extra ground wire between the case of the gen and the base of the reg would be a good test.

What I can't recall just this moment is if your gen is a 3 brush unit in which case your 3d brush needs to be moved to lower the charging rate. If not, and the ground wire does not make a difference, then your regulator needs adjustment or is mismatched with your generator.

That was what I was wondering if it might be a 3 brush generator?? Pictures needed.

Was the generator repolarized after replacing the regulator?

Original equipment on the 1936 "120" was a third brush type generator where the amperage output is controlled by adjustment of the 3rd brush, not the regulator. Voltage is controlled by the regulator.

PS - 10 volts at the battery can prove very damaging.

Battery seems good so far. Holds the 6. Volts after sitting for weeks.

No, I have not yet repolarized. I do see that the ammeter drops when I hit the lights, so I figured it was correct. Honestly that was a second question I had is how to do that if needed.

I will check grounds as well. That's a good idea.

I'm also not sure on the brushes. I will go to the garage today to get pictures.

Thanks for all your responses!

Owen, did they use just a cutout for a regulator on these? I know some three brush generators only used a cutout and the rest was controlled by the setting of the third brush. John

Pretty much the same functionally as the senior series, the cutout also incorporated a voltage control.

Here's a few pictures.

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