55 Generator Problem

[Fenwick B.]

I'm am not getting any voltage output from the generator on my 55. I've polarized the armature by using the instructions that I got off of the board, and I still don't get any output. The voltage on the Armature and the Field to ground are both about zero. I am getting about 1.5 Ohms to ground on the armature treminal, and about 7.2 Ohms to ground on the Field terminal. I get about 5.6 Ohms from the field to the armature. Does anyone have any idea what the problem is, other than a bad generator?

[Jim L.]

Re: 55 Generator Problem

I'm am not getting any voltage output from the generator on my 55.

An easy, quick check of the generator is to ground the field terminal while measuring Voltage at the armature terminal. If the generator is good, this ought to net you about 9 Volts at the armature.

Jim

[Fenwick B.]

Re: 55 Generator Problem

Jim, I grounded the field, and got about 11 volts on the Armature. It went up to 14 volts when I raced the engine. The amp meter showed that it was charging also. when I removed the ground from the field terminal the amp gauge went into the negative range, and the voltage went down.

[Jim L.]

Re: 55 Generator Problem

Good generator. Bad Voltage regulator (or interconnecting cable).

Jim

EDIT: Brain spasm. '55 V8 is, of course a 12 Volt system, not a 6 Volt system like I was thinking when I wrote the earlier posting. 14 Volts is a good value for generator output and could have gone even higher with higher engine speed.

[Fenwick B.]

Re: 55 Generator Problem

Thanks for the help. I'll check it out.

[Roy B.]

Re: 55 Generator Problem

It sounds like The generator is not grounding to the VR

[Richard M.]

Re: 55 Generator Problem

Sounds like a regulator, but..........
You can test the generator by running it as a motor.

1- Remove both the positive & negative cables from the battery.

2- Remove the generator belt.

3- Remove the regulator wires from the generator.

4- Connect the Field terminal(F) to the generator case(ground) with a suitable wire.

5- Connect the battery neg- to the generator case(ground). If you have a ammeter add it in series to this circuit.

6- Connect the battery pos+ to the generator Armature terminal(A) to motor it.

If the generator is ok it will run. You should get a reading on the ammeter of about 4.8 to 5.5 amps for non-tach drive, 5.2 to 6.2 amps for tach drive. This is at 12 volts at around 850 to 1100 rpm. Specs from the 1958 & 1961 service manuals.

Rich

[Chuck G.]

Re: 55 Generator Problem

It sounds like The generator is not grounding to the VR

That would be my guess too.

Chuck

[Fenwick B.]

Re: 55 Generator Problem

I replaced the voltage regulator, and it fixed the problem. I may have not been getting a good ground on the old regulator, but changing the regulator cured the problem and i'm going to "let well enought alone". Thanks for tall the help.

[Roy B.]

Re: 55 Generator Problem

I replaced the voltage regulator, and it fixed the problem. I may have not been getting a good ground on the old regulator, but changing the regulator cured the problem and i'm going to "let well enought alone". Thanks for tall the help.

Here is your 55 VR and the correct design

[Jack H.]

Re: 55 Generator Problem

Is it possible you have unrealistic expectations? Generators have a 'cut through' profile meaning they do NOT produce charging current until you rev the engine appropriately to climb above that specific generator's 'cut through' curve.

Modern alternators have a VERY reduced cut through profile and will exhibit some form of charging once they've been reved and allowed to fall back to idle RPM. I've posted the 'cut through' tutorial graphic from the P&A Catalog previously and the DB doesn't want me to duplicate the picture upload. So, you need to search the archives to find/read the graphic...

Bottom line, don't expect to see output from your generator until you rev the engine into the 1500-2000 RPM range!

[Fenwick B.]

Re: 55 Generator Problem

Thanks again for all the help. I put about 75 miles on it today, in the 100 degree heat. The car did a lot better than I did. I had been looking at the amp gauge for a while and I thought that it was not charging, even though the battery wasn't going dead while driving it during the daytime. I drove it at night a few days ago and determined that it wasn't charging. It charged today because the battry was still not fully charged yet. I have a $23.00 Autozone replacement regulator in it, until I get a Delco replacement.