i cant park my car and come back and start it up again with out disconnecting the battery cables. it seems that somewhere something is draining my battery when it is turned off.

i have checked all my features that could be switched on but found nothing. any ideas or is there a way i can check things to see if they might be staying on.

also is it normal for an alternator to get super hot, in any driving condition(at idle, street cruising)??would a bad alternator draw power from the battery?

What kind of vehicle?

Could be a bad alternator as well as a lot of other things.
You need to do the test for finding a parasitic drain on the battery.

http://www.chevelles.com/forums/showthread.php?t=182746

http://www.chevelles.com/forums/showthread.php?t=167900

http://www.chevelles.com/forums/showthread.php?t=136462

http://www.chevelles.com/forums/showthread.php?t=133604

http://www.chevelles.com/forums/showthread.php?t=54232

http://www.chevelles.com/forums/showthread.php?t=52838

its a 72 malibu. not very good with multimeter testing but i have one and i guess this where i get to learn. ill keep reading through these threads and see what i can do.

thanks so much, now i have a place to start

You can use a test light.

Ben,

You have a shorted diode in your alternator. FYI, There are three diodes in the typical GM alternator. If you look at the back of the stock GM alternator, each of those round circles you see there are a diode. Start with a cold alternator. Run the engine and put your fingers on each of the diodes...or use a temperature probe if you have one. The shorted diode will very quickly get hot.

FYI, if any of the three diodes go open, your alternator merely puts out less current. If, on the other hand, they short to ground through the case of the diode, then they draw current at all times. If you have a shorted diode, it will get hot, and that's where your battery current is going. My bet is that is why your alternator is so hot when running.
Once upon a time, when dinosaurs roamed the earth, you could buy the replacement diode cage for about 8 bucks. :-) Dunno if you still can. Much cheaper than replacing the entire alternator, though.

Cheers,

CBG

Disconnect the negative terminal from the battery. Connect a test light between them and start pulling fuses. If light goes out thats the circut with the problem.If not GM alternators had a problem with diode trios that can be replaced.

I know this is an old post but a related question on the diodes.

Will they only discharge when the alternator is in a specific parked position or do they leak all of the time when bad???

I know this is an old post but a related question on the diodes.

Will they only discharge when the alternator is in a specific parked position or do they leak all of the time when bad???

http://www.classictruckshop.com/clubs/earlyburbs/projects/trouble/alternator.jpg

All the time...

So, if I understand this right.. If you disconnect the wire between the alt/battery and place a test light in series, if the lamp lights you have a diode issue; if it does not then all is OK????????::confused:

So, if I understand this right.. If you disconnect the wire between the alt/battery and place a test light in series, if the lamp lights you have a diode issue; if it does not then all is OK????????::confused:

Not exactly. If the light lights you have a bad diode or SOME OTHER power drain. The test suggested isn't specific to bad diodes.

Most auto parts stores can test your alternator output with the car running which tests the diodes specifically.