Rocketowner

Started to a show on Saturday, and car would've start. Jump started just fine. Drove 40 miles to show, had to jump start before driving home. Charged battery, checked good 12.88, checks 12.82v at battery tab of voltage regulator,but testing large post (on generator ) get 0. Shouldn't there be 12v going into generator? This is on my '55 Olds. Larry

stellar

Large post on gen should be 0 when car is not running.

Rocketowner

Thanks Stellar,I wasn't sure.Read your profile and you should know.Experience helps. Larry

47 Convertible

Did you find the source of your trouble? I'm curious to know as more than once a similar situation has turned out to be a battery with one or more cells kaput that will show 12+ volts right after a charge but then won't hold a charge. In your case the generator or voltage regulator might be suspect as well. Let us know please.
Jerry

droldsmorland

Whats the running voltage at the battery positive post? Should be 13.2ish - 14.2ish VDC. How did you "check" the battery? A Load test is the proper way to check a battery. Buy a load/charging system tester. $60-70 at Pepboys, Schumacher makes a good one see pic. If the battery load test good and the Generator(or alt if you converted it) output is as stated above then look at the regulator and starter and grounds. Tap on the alternator/generator with a 2x4. See if it wakes up. May need brushes or diodes? How are all the grounds under the hood? If this cars never been apart those are likely 60 year old grounds.

Rocketowner

I just pulled my generator off and the brushes are worn down very short to the point that there's not much tension between them and the armature. I am going to install a new set, clean and sand the armature, and I'll report back my results. Concerning the battery ,it's only a year or so old ,but I had it tested at Advance where I purchased it ,and the machine they tested it with gave a print out that it was good.Also tested it with tester that looked like the one shown above, and it showed no charge was going into the battery(same as battery tested not running). Thanks Larry

47 Convertible

Sounds like you are on the right track eliminating potential trouble spots in the right order. The brushes might be the fix but as long as you are at it check the wiring too and particularly the grounds as droldsmorland suggests.

FWIW I had a 3 yr. old NAPA battery go bad on me recently. It tested good on their in store tester which supposedly put a load on it to check for weak cells. It would barely turn over the rebuilt 461 and I thought something must be too tight in the engine assembly. As a precaution I had a trusted mechanic friend test the NAPA battery which turned out to be no good. A new 800 CCA battery has the BBO spinning over like a sewing machine and firing right up.

rustyroger

A quick and dirt check for a suspect battery is to have it fully charged, then turn on the headlights for 10 minutes without running the engine. If it still shows good voltage then it's probably ok. Not foolproof, but might help if you are stuck in the Boonies without much in the way of tools or help.

Roger.

Rocketowner

Thanks again for all your interest and help. With generator on the bench,I placed sandpaper between the brushes and armature,turn it 3 or4 rounds by hand,blew it out.Carried to the rebuilder this morning,he put it on the machine and said it checked good.Returned Home and put it back on and checked it with the car idled up to 1000 RPM's and it should 13.8 on the multimeter. Guess it was just corroded between brushes and armature. LARRY

droldsmorland

Good news. Again I cant stress enough to make sure all the grounds are clean and tight. You should have a secondary strap or 4 gauge min wire from the engine to the body and engine to frame. This will insure that the system isnt struggling especially once hot. Take a good look at your battery cables. If they are older then say 20 it could be time. They can look good but have high resistance. This will over work everything and can lead to premature failure of everything that runs off the battery voltage...starter, alt/gen VR etc...