Why is my Mazda MX-3 losing all battery power whenever lights are used?

Hi everyone,

I'm having a big problem with my '96 Mazda MX-3. One day I suddenly lost all the power to the battery and I figured the car was no longer charging. I changed the alternator (used part from salvage yard) and it drove fine for a few days then went dead again. I changed the battery, and it also drove fine for a few days then went dead again. I ran a new wire from the alternator to the battery's positive terminal, assuming that since the alternator was new (to me) and hopefully putting out power that maybe it just wasn't getting to the battery from a bad wire somewhere. That seemed to help the voltage and the car ran great and I could run my system and all until I got halfway to my destination and everything went dead again.

What I had noticed is that the car would run sitting at an idle, but would drain when I drive it. I just discovered today that this is because the lights are draining the battery, and the car has driving lights that go on as soon as the E-brake is released. So I started driving around today and with the E-brake slightly engaged (to cut the driving lights) and if I lay off the signal lights and brake lights (thankfully the car is a standard and I hardly ever use brakes on a standard), that the car seems to run fine. Of course, that's also leaving all interior accessories off as well (ie, radio, heater fan, etc.).

When I test with a voltmeter (though my voltmeter doesn't seem too accurate anymore) I get a slight raise in voltage when I initially rev up the engine but then that goes down and actually LOSES a little voltage when I continue to rev.

Please, do any of you experienced Mazda owners know anything that could cause these problems? I haven't a clue anymore.