Could use some help with this problem....thanks in advance!
Car operates well when driving, but when parked for 30 minutes or more, battery loses charge. When operating, amp guage indicates that battery is charging, so I feel the generator is outputting. Upon re-charging the battery, the car starts immediately. The voltage regulator is brand new and the battery tests good. If the negative grounded battery cable is diconnected, the battery stays charged.

I did replace both water pumps and the fan belt since one water pump was sticking and the belt was slipping. This was a more recent development, however.

It appears there is a direct short somewhere which is totally draining the battery.Anybody have any ideas.....?

Put one of those battery disconnects on it. When you stop the car disconnect battery. If the problem goes away with this procedure then start looking for a short. If problem persists then you may have a bad battery.

Negative ground on a '40 Ford?

Biggarmike might be onto something there. A '40 Ford should be Positive ground.
You can check for draw by disconnecting the ground cable and connecting a test light between the post and cable. if there is a draw, the test light will light. Then start pulling fuses one at a time until the light goes out, and you know what circuit to check.
On that old car, you probably don't have a lot of fuses, so you might just have to start disconnecting different electrical components until you hit the magic wire. When the light goes out, start checking everything in that circuit until you strike gold.

You are absolutely right! '40 Ford Flathead is positive ground. I should have remembered that from my high school years in the 50's.

Thanks!

Hey RocketDude!

BiggerMike is right. '40 Ford is positive ground. Thanks for your help! I will try what you have suggested.

Thanks! I'll take your suggestion. If it works it's a pretty inexpensive solution.

Best regards!

Don't forget to polarize your generator, if you've been discharging the battery through the generator, you will need to. (another thing, make sure you didn't burn the contacts in the regulator, if you are still running a mechanical one)

Biggarmike,

Great info.....thanks!