just replaced an alternator on my friends 2001 prelude SH. it runs fine now, but when i come to a stop and the car is idling, the battery light and brake light (on the dash) comes on. if i hit the throttle or once i start driving, the lights turn off. i thought it was a defective alternator so i tried another good alternator, and the same thing is happening. anyone know what this could be?

 

First off, manually test the battery voltage with a voltimeter. Make sure it's close to 14.5V when the car is on, if it's not u got a problem. If it is, check all the connections, the cable going to it, the green 4 pin connctor, all the way back to the fuse box.

 

My car is doing the same thing, and my raido has a built in battery meter that says over about 1500 rpm or so I'm at 14.2 volts but at idle I'm only at 12.2 volts. Any suggestions?

 

possibly a bad ground to the battery or alternator. or just bad battery.