I had an alternator that charged just fine, but I had the same problem as you. It will go dead after a couple weeks. I took the alternator to my buddy who owns an alternator shop. He said it had a bad diode in it which would cause it to drain the battery.
I had the problem when I first got my '69. I had to disconnect the neg. battery cable every time I parked it until I did a draw test. I did it using the negative cable as I read it was preferred over the positive cable. Placed my meter between the post and cable. Had a draw. Checked fuses and found the circuit. It was my power top switch. All I did was move it back and forth a couple times and the draw was gone....I guess it wasn't used much and was stuck enough to draw power but not be connected enough to work. Has been fine since.
Dirty batteries develop a conductive slime on the case; the battery can discharge from the current carried by the slime between the two terminals. Easy to test for. Put one voltmeter lead on one post--let's say the negative lead on the negative post. Then take the other lead, and drag it along the case in a circle on the plastic around that same post--negative in this case. If you see more than one or two volts, you need to clean (and dry) the battery case. Common for the voltage to increase the closer you get to the other battery terminal--positive in this example. Used to be, dashboard electro-mechanical clocks were a frequent cause of dead batteries. The winding motor inside them is supposed to be an intermittent power draw--the motor runs, winds the clock spring. Motor stops. Clock spring powers the clock for a minute or two, then the motor runs for two-three seconds to wind the spring again. Spring breaks, motor runs continuously until it fails. Drains the battery in the process. Once in awhile, I'd see an electro-magnetic external voltage regulator with welded contacts. Alternator doesn't charge properly, but the alternator tests fine at the parts store, because it's no longer connected to the failed voltage regulator. While it is connected, there can be a current drain through the welded contacts and relay windings. Beyond that, all the usual suspects have been covered--faulty alternator diodes, faulty aftermarket crap--or faulty installation of aftermarket crap. Power accessories that don't turn off when they're supposed to. Watching an ammeter while pulling fuses can work really well. Then you run into a problem that isn't on a fused circuit. Perhaps something powered by a fusible link, or a circuit breaker. In that case, you could remove all the fuses, and still have the power draw.
Agreed Schurkey . I've seen the battery drain across the top of the battery from the negative post to the positive post . I never tried a side terminal battery but I've seen upwards of 8 volts across a top terminal battery .
I had to update everyone since I found what was causing my problem. The horn was draining the battery although it was not making any sound. After removing the contact from underneath the horn button (billet steering wheel) the battery no longer drains. Thanks for the help.
I hate to agree, but I DO agree I understand young people need jobs, but some jobs "training" just isnt enough. In the automotive field, you need "natural ability, and interest" If these younger people cant test your parts using Facebook, Spotify, tweeter, or some other app. they're useless in the parts store.
Check your interior lights when car door is closed. I had a few 76-77 cars. When hinges get worn the door switch doesn’t always close. And interior lights stay on. .
