I recently purchased a 1964. For the past several months I have been repairing and replacing the botched repiar attempts made in the past. So far I have replaced the entire wiring harness (old one was a fire waiting to happen), all gauges, voltage regulator, horn replay, ballast resistor, battery, rebuilt headlight motors, rebuilt wiper motor and repaced ignition, light and wiper, horn and turn signal switches, as well as the lighter.
I took it for a 70 mile round trip and noticed that the ammeter was showing a discharge. My return trip was after dark and the headlights were very dim. As I got about a mile from home the engine began to misfire and the turn signals would not function. When I got home and turn the ignition off, it would not even crank.
I had the alternator (not original a 61 amp Delco reman I suppose)tested and was told that it was one of the best they had tested and I replaced the voltage regulator, again. Now when it is running the ammeter is a notch or two in the discharge side at idle and stays there as the rpm is increased. When the lights are turned on the ammeter show a large discharge and does not show any recovery.
What am I missing?

 

Here is an article I wrote that describes the charging system and how to diagnose it.
If you have any questions I will try and answer them.
Joe

http://temp.corvetteforum.net/classi...ternator.shtml

 

A simple test: Hook up a voltmeter to you alternator and see if you get more than battery voltage with the engine running. Then try this test, it will bypass the voltage regulator.

 

any other comments?

 

I'm not sure I have the answer, but I had exactly the same symptoms on a '65 that I rebuilt from the ground up a number of years ago after it had burned up in a fire. After I got the car drivable but not yet fully assembled, the battery would go dead after a few weeks even though I would start it up at least 8-10 times a week and every few days would drive it a couple miles on local streets. Here are the notes from the diary that I kept:

Finally got the Alternator to work. I thought at first that the Alternator was shot because ammeter showed no charging. I even tried replacing the alternator and voltage regulator but to no avail. After looking at the wiring diagram in the assembly manual, I determined that Horn Relay had to be installed to provide connection between Voltage Regulator and Battery. Problem solved!

I'd suggest that you check against the wiring diagram to see if you have a missing wire or connection between the voltage regulator and battery.

 

i agree check the wiring between the vr and the alt for a bad or loose fitting or an open wire...good luck

 

Thaks everyone for the input. I have replaced the alternator with the same results, I will conduct the test mentioned this weekend. Although the battery is not yet a year old it has gone dead once prior to the discharge the other night so I will test it also.

 

I was driving home, when I noticed my battery gauge was discharging, instead of the usual charging, particularly with the headlights on at night. I suspected the alternator, and when I got home, I removed it and took it back to Advance Auto Parts (formerly Discount Auto Parts), where I had a lifetime warranty. They tested it, and sure enough, the alternator was bad. Got a new one for free! But the new one didn't seem to be charging at idle, only when I got the RPMs up over 1600. I ran through the diagnostic procedure posted here, and it pointed to the alternator. So I took it back and got another new one (even tho AAP tested alternator, and it was fine). Same thing. Long story short, it was the voltage regulator, not the alternator. In particular this step of the test was failing:

"There should not be any voltage at the other three terminals at this time. If you have voltage at the number 2 terminal, R on the alternator, you have a leaky diode in the alternator, replace the alternator."

I had about 6.3V (1/2 battery voltage) on the number 2 terminal. But after replacing the VR, everything seems fine. (AAP alternators come with a note to replace VR every time you replace alternator- and the salesman insisted I do so, before he would give me a 3rd alternator. He offered to refund my money.)

Anyone else notice similar results? I repeated the test with the alternator out of the car - and a bench power supply - same results - pointing to bad alternator.

- David Knowles
'67 L36

 

Thanks for all the input. Plaidside thanks for the article, it was most helpful. After conducting a number of test as well as having the battery and alternator tested at two locations, I began to suspect the new wiring harness. The problem was reversed wiring on the alternator connector. Field on alternator went to #2 on regulator and Relay on alternator went to field on the regulator. I put the wires in the correct positions and tghe ammeter shot to + when the engine fired. Battery is staying charged and Mid-Year life is good again. Again thanks for the help.