alternator dead?

[applewew]

Hello,

Today I found the battery dead. I started the engine by pushing the car, but as soon as I stop giving it gas, the engine stalls.

Background:

It happened before that I find the battery drained, but not completely dead, I start it by pushing the car, the battery charges and it works ok. But it has drained at least once a month.

I switched the battery recently with the one from my truck, and removed the door open alarm/buzzer in case it was activating randomly (wich happened some times before).

//

Is the alternator dead?

[splatterdog]

If not it will be if you keep charging a dead battery with it. The alt might be OK since the charge and brake light aren't on. Sounds like there is a draw on the battery, something running after the key is off. A bad diode in the alternator can do this too, and still charge(weakly). Got a volt/amp meter?

[marlinh]

Make sure the interior light hasn't been left on. Door switches all work if it isn't manually switched on. Not so noticeable in the summer.

[applewew]

But if the alternator is OK, shouldn't the engine run fine (not start) as long as I don't remove the battery?

[MR2Di4]

Simplest way to check is putting a multimeter (volt/amp meter) on the battery terminals with the car running. You should be getting around 14 volts or so if the alternator is working. If not your alternator is probably bad. (bad brushes, windings or most likely a regulator) I just had mine go out suddenly, the car had been sitting a long while and it worked when I got it, but now I get no voltage from it, even after pulling the charging wire off the alternator and testing it's output by putting the positive probe to the terminal on the alternator and the negative probe to ground.

In theory, the car should still run even without a battery if the alternator is ok since it's supplying the voltage for the ignition coil. The battery is just there for storage and capacitance to help even out the supply of voltage to the car's circuits. But also keep in mind that an alternator also requires a battery source to start producing electricity and that it's very hard on the alternator and putting any heavy draw like headlights or electric fans would likey overload it and cause the car to die.

MR2Di4

[applewew]

I just started the car with another battery and then removed the battery.

It continued to run, but the lights dimming constantly, then I pushed the gas pedal for a while, and it died on the instant I removed by feet off the pedal.

[Petros]

a batter that is has a short can act that way, works but will not hold a charge for long. Sounds like the alternator is questionable, also verify the ground both on the engine and the battery terminal (both ends) is good and clean, and the one on the engine. You might just have an intermittent ground.

before you just replace the alternator you might take it to a local auto parts store, most will test it for free (NAPA and Autozone).

I drove from California to Washington with a battery with a bad cell, would not have enough juice after a gas stop so I always made sure I could roll out of the gas station to get started. Got it home, pulled the caps and than put my volt meter probes into each pair of adjoining cells in the battery, all had 2.2 volts, but one. ONe dead cell means it was a bad battery. If you do this to test your battery, make sure you do not allow the probes to touch the plates, put them in the liquid only.

[celtglen]

I just started the car with another battery and then removed the battery.

It continued to run, but the lights dimming constantly, then I pushed the gas pedal for a while, and it died on the instant I removed by feet off the pedal.

I would also take a look at the voltage regulator, mine is not inside the alternator, but yours may be inside the alternator if it is a 4wd.

[applewew]

Mine is a 1985 2wd hatchback.

It happened to be a combination of the Alternator and the battery.

The battery happened to be "cold" and required deep/slow charge (that's what the electrician said). I got the alternator fixed, but also got a new one. So the fixed one is a backup now.

[teranfirbt]

Bad wiring can be a killer to the charging system... My dad went through 3 alternators and 2 batteries on his old Talon before he found a loose ground strap that cured the whole problem.

[celtglen]

Make sure the interior light hasn't been left on. Door switches all work if it isn't manually switched on. Not so noticeable in the summer.

Or if your windows are "filmed" rather darkly..happened to me just this evening..luckily I caught it before I locked her up for the night