Okay, so I recently bought a brand new battery from Walmart (about a week and a half ago) when my last one died and then installed a new alternator (about a week ago) in my car. I was driving into Macon when I noticed both my speedometer and tachometer going crazy in my car. When I took my foot off the gas or had it out of gear, they would bounce around back and forth from 0 to whatever it had been reading before. It would do this once or twice, then stop. I kept going and got further into town. Later, I noticed that when I had it out of gear and my foot on the brake, the tach and speedometer would read zero. Then, as soon as I took my foot off the brake, they'd go back to normal. It was about this time that I noticed other things acting strangely. The lights in my dash became dimmer and dimmer, my radio got softer, and my engine idled lower and lower. When we checked the battery, it showed 11.25 volts on it. When we took the alternator to AutoZone (where we got it from), it passed all of their tests. What's going on?

Add'l. info: '95 Honda Civic, 1.5 ltr 4 cylinder engine, manual transmission.

 

The alternator is not charging the battery. First, is the belt on properly? Then check that it has a connection through the car wiring. On the alternator, the big white wire should have battery voltage all the time. That comes through the fuse box under the hood. The "I" wire (black and yellow) in the 4 wire plug should have voltage when the key is on even with engine not running. That comes from a fuse under the dash. The "battery" light on the dash should come on with the key on engine not running, and go out after it is started.

 

Thanks for the info. I know this sounds like a ridiculous (and probably stupid) question, but I'm new at this, so it's allowed, right? When I'm testing those wires, where would I put the leads? Obviously one end goes on the end of the wire in question, but what about the other? The battery? If so, which terminal? If not, where?

 

Put the black wire of your meter on a grounded metal part, either the engine or battery (-).

When testing inside the car (e.g. probing switches or fuses), the outer shell of the cigarette lighter is a good place to ground your meter.

 

Turns out that my battery was bad. On a whim, I took it down to O'Reilly's just to have them charge the thing (and remove it as a possibility). I returned thirty minutes later, and he told me that the battery would not hold a charge on his machine. The guy explained to me that some stores forget to change out the old batteries on their shelves, and I could have just been given a bad one. I got it from Walmart, so that probably explains it. When I put the new one on, I tested it running. 14.25 at the battery and 14.25 at the alternator. Hopefully this is the last I'll see of this issue for a while.

Thanks for your help.