I'm having problems with my '66 not holding a charge...

My GF took it to work and left the lights on overnight. Needless to say, I had to jump it. It made it about two blocks before dieing. I replaced the battery while it sat on the side of the road (no idea how old the other battery was). After taking it to and from work a couple of days it wouldn't start. It just made a ticking sound like it did not have enough power to start. So I mad an assumption...the altenator was bad. I took it off and had Autozone test it. It failed miserable. Replaced the altenator. Took a couple of drives with the (now) "new" altenator and battery. It died while sitting at a traffic light. Everyone I talked to said I should replace the voltage regulator (why not, I need to replace a lot of stuff on the car anyway. Did I also say the ampmeter doesn't work). I checked the voltage across all connections and they tested between 11-13 volts (DC). Again, I took it for a couple of drives before it died again (and wouldn't start without a jump). The only thing I know to do now is check/replace the ground wiring.

A few things to note...
When I replaced the altenator, the wiring doesn't really match any schematics I've seen for the '66s, so I'm kind of worried that maybe the wiring is wrong. I haven't had a chance to trace out the wiring, but I hope it's right. There is only one place to attach the battery connection to the alt (it's the only one that fits). The battery wire is yellow/black, the "neutral" wire is yellow, and the other wires (this is where is differs...there are 2) are black.

 

I had the same exact problem....check to make sure the wires are on really tight on the back of the alternator.....and definitly replace the voltage regulator.Cant go wrong and it is cheap...12 dollars...two screws and one wiring harness....easy cheap fix. Scott

 

This is an all too common scenario. Please take no offense.

So many people insist on starting to throw parts at such a problem like shooting in the dark instead of scientifically troubleshooting and identifying the problem. If you have no idea how to properly troubleshoot such a problem, pay someone who does know how and you will be money and frustration ahead.

Here are some basics.

Starting system. If it won't crank or cranks slowly, use a digital voltmeter on the DC scale across each leg of the circuit thinking of each leg as a link in the chain. With your voltmeter leads across each link, such as between the positive battery post and the input post to the solenoid, have an assistant turn the key to the start position and note the DVM reading. If the reading is high, like 9 volts or better then the weak link is between your battery leads. A high voltage is telling you that there is a high resistance at that point. If you have very little voltage across that point, then go to the next link and do the same thing at each link down the line. When you find where a high voltage is read THAT is your culprit.

Charging system. Begin by putting both leads across the battery and having the assistant rev the engine to about 1,500 RPM. You should see about 13.5 to 14.5 volts if the alternator is charging, if you only have battery voltage (about 12 volts) then the alternator is not charging. If it is not charging, do the voltage drop test again across each link in the alternator circuit chain. When you find the high voltage, that is your resistance, meaning the bad link in the chain.

Hope this helps.

Troubleshoot the problem rather than throwing parts at it, you will be better off every time.

 

this is my exact problem, exept mine wont start with a jump...

 

Dam the stock alternator and Voltage regulator. Put a big 1 wire alternator on there and run 1 wire to the hot side of the battery and you are done. I know this doesn't help you in your situation, but it is a simple fix if you have doubts or concerns about old wiring and charging systems.