daem0n

So, I recently replaced my battery because the parts store told me it was dead (it's ok since I had a free replacement warranty)...but now it turns out the problem is not my battery.

I can jump-start my car and as long as the battery is hooked-up I can run the car pretty well for as long as I need, until I shut the engine off. Then, I can't restart the car because there's not enough reserve power in the battery.

Someone said that you can test the alternator by disconnecting the negative battery cable while the car's running and if the car dies, then it's most likely the alternator. Well, I did this test and it seemed to be running ok until I applied the brake pedal and the car immediately just died.

It's been suggested to take the alternator to a shop and get them to test it but I don't have any shops around that I trust (especially after the replacement of my other battery). So with that in mind, is there a way to test the voltage coming off of the alternator...and if so, what voltage should it be, etc?

Thanks for any and all help! -Joe

bryant

my haltech reads about 13.9
autozone or any true parts store can test the alt.

rotor rod

You can check voltage @ the battery with the car running. You should see anywhere from 13.6 to 14.2 volts @ the battery.

Keeping the battery terminals on ofcourse.

DomFD

ya you can test battery at AZ... but if you alternator is out wouldn't your car just run off the battery power? and that would usually just last like how much 10-30mins?

daem0n

Do you think that you should get the same voltage if you disconnect the battery and then test the cables that "should" be connected? This way you're not also testing the voltage coming off of the battery. Is that thinking correct?

rotor rod

Yes, you wouldn't last too long on just on battery power, I broke an alt belt once and made it only about 7 mi.

I'm thinking maybe a poor, or no connection from the alt to the batt. That would would explain why the car is ok after starting. Maybe the battery is not getting any charge and the cranking killed the new battery.

rotor rod

The easiest way is to just see how much voltage you have at the battery with the car running. If you see around 12V, the alternator is not charging the battery, if you see between 13.6 14.2V then you are getting a charge from the alt.

daem0n

ok thanks for the help. I will try that out as soon as I find my multimeter :P