Battery draining?

[Yakinho]

So the other day I go to start the car and it cranks one time and then nothing... roll down the hill, pop the clutch, go to work. I put a new battery in last Wednesday and everything was good until today. I heard it losing power (slower crank) and figured it would just be fine if I kept driving... My question is what could be draining all the juice? when I turn the key to position 3, everything works except the ignition, it cranks once, then half a turn.... windows, lights, everything else works...

[Yakinho]

bump.... Hate to bump a half an hour later, but I really need this fixed ASAP.

[PiercedE30]

Break out the multimeter. Pull out fuses one at a time and see if there is any voltage going across where the fuse would be. When you find one, look at the system that the fuse controls and move from there.

[asubimmer]

alt good?

[Yakinho]

Thanks for the reponses. Alt should be fine, it wouldn't drain battery, right? Time to pull out the flashlight, fucking daylight savings.

[jlevie]

Since you just replaced the battery, double check the connections. A dirty or loose connection can cause this.

There is a failure mode of the alternator that will drain the battery. That and other failure modes will prevent the alternator from charging the battery. A quick check is to see what the system voltage is with the car idling and at 2500rpm. At idle you need to see at least 13.5v and at 2500rpm you should see about 14v.

[franco90]

BAD alternator is the problem. it happen to me take the your ride to auto zone to test battery/alternator is free.

[Mr.sexymorningvoice]

Make sure that when you are getting a battery that is has some pretty good cranking amps(cold cranking amps actually)...because with a battery in the trunk and tose long ass cables, the resistance really kmocks the voltage down, and with the lower voltage means pre-mature starter failure. I peraonaly have a 960cca amp battery out of a road tractor, not to mention it fits in the hole perfectly...

[Yakinho]

Did some checks and it must be the alternator. Battery is good, runs my dads M635, 633, 740, van, etc... I charged the battery and it does hold charge but each start is a little weaker. Cables are fine. I shouldn't have problems finding an alternator for this car, should I?