new battery drains, no reading on ammeter...

[tsherry]

This is in a '67 F250 CS. I installed a new battery, which was drained in a day or so. I've recharged the battery, hooked up the positive post, and checked each circuit that goes through the fuse block by pulling the fuses, hooking up a test light between the negative post and the negative cable, and systematically reinstalling the fuses.

In no case, with the exception of the dome light, did the test light come on. I closed the door, test light and dome light went off.

Any ideas on what could be draining the battery? Internal short inside the alternator or something?

thanks--

tom s.

[Mohillbilly]

Was this happening before the new battery install, or only since then. I've had bad batteries, starters, etc fresh from the manufacturer before. Does it drain just sitting and turned off, or while it's being driven? A bad diode in the alternator could cause it to drain while running, or a bad voltage regulator could cause it to drain when turned off. If it takes all day to drain, it could be a high enough resistance short to not light a test light. A meter might be necessary. Good luck.

[19674x4]

alternator or voltage regulator or you have a short some where

[tsherry]

Was this happening before the new battery install, or only since then. I've had bad batteries, starters, etc fresh from the manufacturer before. Does it drain just sitting and turned off, or while it's being driven? A bad diode in the alternator could cause it to drain while running, or a bad voltage regulator could cause it to drain when turned off. If it takes all day to drain, it could be a high enough resistance short to not light a test light. A meter might be necessary. Good luck.

It was happening before the new battery was installed--the old battery was eight years old, and I thought it was a 'battery problem' at that point. It drains while sitting....but then again, I haven't double checked alternator output. That, maybe tomorrow. Good call on the high resistance idea. Hadn't thought of that...I'll take out the meter.

[rjewkes]

also if your electrical system checks out, althought it wouldn't drain while sitting a starter with the nose cone broke off would drain all power at startup.

[jzjames]

...check your brake light switch???