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57 Generator Advice Please

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Old 08-09-2017, 02:37 PM   #1
C.T.
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Default 57 Generator Advice Please

57 270, all stock. Always on tender. Very low annual miles, none at night.

Cranks and starts fine when leaving the house, but last few times has cranked slowly when re-started to return home. Battery 7 years old, but thought I should check the charging system before replacing it. Searched the invaluable archives here and did/found the following:

Engine not running, tender disconnected, battery voltage 12.98 using VM; polarize generator

Start engine, battery voltage 12.61 at idle, no increase with higher revs. Momentarily ground Field terminal, battery voltage 12.58

With VM positive to Arm terminal and negative to ground, momentarily ground Field terminal, get 1-2 volts

With VM positive to Arm terminal and negative to ground, with blue Field wire disconnected, get 1-2 volts at fast idle, 12 volts and rising at 2500 + RPM.

So the generator is bad? Puzzling because it is a rebuilt unit (same for regulator) although it sat on the shelf for a few years. The wiring is new and connections are good. The ammeter shows a reasonable discharge with lights on, but stays at '0' otherwise, including at higher RPM. The wiring manufacturer said this is normal with a good battery.

Only other item I noticed was a faint 'click' from the reg when I polarized the gen, then a louder click when I disconnected the battery. I always disconnect the battery when not driving and haven't heard any clicking before.

Should the gen and/or reg be replaced, or? Thank you all very much for your input!
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Old 08-09-2017, 02:53 PM   #2
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Well clearly the circuit is not charging. Check the generator brushes before you panic and start swapping parts; sometimes they crack or hang up in their housings or are just worn out...
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Old 08-11-2017, 03:29 PM   #3
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Frankie and others -

You nailed it! I took the generator off and found the brush on the field side cocked in its holder so it wasn't touching the commutator! I put everything back together and got these results:

Battery volts 13.11 (was on tender night before), polarize gen
Tried to start, slow cranking, jumped battery, started. Volts at battery 12.54, with higher revs 12.91. Ground field terminal at fast idle, volts rise from 12.58 to 18. (So gen good, reg bad?)
Disconnect field, connect VM to arm, .4V at higher revs (So bad reg?)
Connect VM to arm, ground field, get 12.7 volts (?)

When the engine was running, I noticed (for the first time ever) the ammeter was showing a tiny charge. I tried the parking lights and got a small discharge, and then the headlights but that killed the engine. There wasn't enough battery to crank the engine.

So the battery seems to take a charge, but not hold it, so it gets replaced. How about the gen and reg? I have a new, rebuilt DR reg thanks to Pilot Dan, but I hesitate to put that on unless you think the gen is ok. Thoughts please!
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Old 08-11-2017, 04:17 PM   #4
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I would put the new V/R on and take the readings again....you won't hurt anything..
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Old 08-11-2017, 07:32 PM   #5
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Quote:
Originally Posted by Frankie the Fink View Post
I would put the new V/R on and take the readings again....you won't hurt anything..
Okay, thank you. Should the battery be replaced first?

Here's a couple shots of the faulty gen brush...
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Old 08-12-2017, 04:50 PM   #6
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Frankie, did the tests again with the rebuilt reg -

Charged battery, volts 13.15, polarize gen
Start engine, volts at battery 12.84, at higher revs 12.84. Ground field terminal, 12.81. (Gen bad?)
Disconnect field, connect VM to arm, .6 volts at higher revs (Reg bad?)
Connect VM to arm, ground field, .11 volts (Same with field not grounded.)

Watching the dash ammeter, pulled on headlights, get reasonable discharge. Revs make no change. Shut lights off, ammeter returns to 0. Revs make no change. Shouldn't I see some charge?

I thought the 'fixed' gen and the rebuilt reg would get good results, but that doesn't seem to be the case. Which (or both) do you think is causing the problems?

Thank you very much!
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Old 08-12-2017, 05:10 PM   #7
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I'm not near my home just now but any of the 58-61 Passenger Car shop manuals have the procedure to isolate the culprit. Perhaps somebody can scan them in or direct you to it...

You really don't have to polarize things all the time...that's only needed if the residual magnetism in the generator assembly is lost and that is rarer than people think.
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Old 08-12-2017, 07:01 PM   #8
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These pages are from the 61 manual but I'm hoping you can read them...took pics with my smartphone and emailed them to myself to post here. They are hi-rez so you can zoom in on them as needed I think...once downloaded.
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Old 08-12-2017, 08:08 PM   #9
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Thank you. I'll try to work through those.

Question for anyone with a stock C1 -- do you ever see a charge on the ammeter? When?

Thanks all!
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Old 08-12-2017, 09:02 PM   #10
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My ammeter always is slightly + when first starting off. I drive it often enough that it's usually not on a tender. I do pop the hood after a drive to vent heat and I use a knife switch disconnect. I recently replaced the battery, it was seven years old. Read good volts, could not crank the starter.
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Old 08-13-2017, 06:22 PM   #11
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Thanks, 64luke, that's helpful.

Anyone else with a stock C1? How does your ammeter behave?

Frankie and others, I did the generator test from your manual: 'Put an ammeter between the reg bat terminal and the reg bat wire. At medium speed, ground the F terminal and gen output should increase.' My result, ammeter stayed on '0' with field grounded or not. Shouldn't some current show?

I repeated the other tests with the same results:
VM at battery 12.67, ground field 12.67
VM to arm .11, ground field .11
VM to arm, disconnect field, idle .2, 3500 rpm .4

These results condemn the gen, and maybe the reg as well. Opinions please! Thank you.
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