Its a 1991 Honda civic and about a month ago my battery died on me while I was working(I deliver pizza) Anyways, I thought it was the alternator so I got the car running, and unhooked the battery and the car ran off the alternator fine.. So I had the battery checked out by canadian tire and they said it was fine... So I thought about it and relised I didnt have a tie down for the battery and it would jump around when hitting bumps, and since I took it out and it shook the lead on the bottom may have evened out a bit.. So I charged the battery and the car worked fine for 1-2 weeks. Then it died again, so I bought a new battery, and now it has died again barley 1 week later... This is what happened, I was driving, and came to a light, and something felt different, and then my music shut off, and my lights started going dim, then my tach went crazy, so I made it back to work and shut the car off, I went to start it again to drive it home and it took a bit but it fired, and after that the lights were bright and everything was dandy... I live in Canada, and its freezing now... Any ideas? The car started this morning after that night as well... And the battery seemed to have enough juice to make the car startup fine... Any help would be great, thanks!

 

Sounds like an electrical short. Given that your tachometer became erratic, you might want to start by checking wires/harness to, from, and within the distributor.

 

Never unhook the battery while the engine is running. That can burn out your alternator, ECU, or various other expensive parts. Check alternator performance using a voltmeter on the battery. It sounds like your alternator isn't always working. Also you may be shaking the battery to death not having it strapped down.

Also I agree with Ron to check your battery connections, ground wires, etc.

 

This happened to my parents' car. It wasn't tied down when it was first installed and they didn't notice right away. From then on it would randomly die every couple of weeks until they just replaced it.

 

Well, I got it tied down tightly with a rubber strap for now, and it doesnt move to much when I try to move it, all the connections look fine and test out okay.

 

*****Its been strapped down ever since I got the new battery

 

Check your alternator belt as well. It might be loose and slipping.

You should be able to tell when your battery isn't charging though, as your battery light should come on on your dash board.

 

Check also that the connections on the back of the alternator and the screws in the underhood fuse box are secure.

You should start carrying around a voltmeter so when it acts up again you can get some measurements.