bad battery? or alternator?

[florida_dirt]

the other night sitting in a parking lot in idle I turned my defroster on and suddenly my car slowly began to die of power... at first my radio turned off then my tachs began bouncing up and down and finally my car bogged down and shut off... I got a jump from a friend and it ran fine until tonight it did the same exact thing leaving my buddies shop... the alternator is fairly new on the car so I don't think that's the problem. unless it's faulty... was leaning towards maybe my battery being bad? previous owner said it was a new battery but it's a cheap no name brand. I'm going to charge the battery out of my other e30 and swap it in then have autozone run a check on my alternator tomorrow ... was just curious if anyone has had this same exact issue and what the results were? thanks.

[kbeefy]

sounds like the alternator isn't charging. I'd first check voltage at the battery with car running, then voltage at the alternator with it running.

Under 13v at the alternator means your not getting much charge, under 13 at the battery means either bad connections or a faulty cable.

If you getting proper voltage at the alternator start looking for bad connections, both on the charge wire and ground connections/straps etc.

[florida_dirt]

sounds like the alternator isn't charging. I'd first check voltage at the battery with car running, then voltage at the alternator with it running.

Under 13v at the alternator means your not getting much charge, under 13 at the battery means either bad connections or a faulty cable.

If you getting proper voltage at the alternator start looking for bad connections, both on the charge wire and ground connections/straps etc.

hey thanks will try and do this tomorrow afternoon if I get a chance.. I appreciate your input

[Nick_S]

Could also be your voltage regulator. Similar problem happened on my car. Battery and alternator both tested fine.

[Poorboyz]

I had that problem on my E46, in my case it was the battery.

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[florida_dirt]

seems to be battery related I feel like the alternator would not just keep giving up and starting up again and it's fairly new... the battery is kind of a shit battery putting a newer one in tomorrow morning gonna see if I have any issues at the end of the day... thanks guys