I have a 1991 Honda CRX HF. Months ago it finally needed a rebuilt alternator installed. Now since the fix when it is cold and for the first few minutes, the battery light comes on. Lately when I drive at night, the dash lights and the headlights go from normal to super bright over and over again. Any suggestions? Thanks!!!

I would remove and fully charge the battery, which most auto parts stores will do for free. Next, I would start the car and check the regulated battery voltage--it should be 14 to 15 volts. If it's not, there is a problem with the alternator. I suspect the problem might be the brushes have worn down too far. They are not easy to replace on Honda alternators and the remanufactures usually don't touch them. Therefore, I wouldn't be surprised if the solution involves installing a new alternator.

Background on battery lights:

Every light bulb has two ends--an end that has voltage and an end that has no voltage. This is how 99% of light bulbs are wired; i.e., power source and ground. As long as the source has voltage, electrons flow, and the light lights up.


The battery light is different. It has two sources--one end is the alternator output and the other end is the battery output. If the alternator is doing its job, it is charging the battery to 12 to 13 volts. This means the alternator output and the battery output are equal. Since the two power sources are putting out equal voltages, they cancel each other out (think sound canceling headphones), and no electrons flow, and the light doesn't light up.


Now, the charging system is very simple . . . there are only a very few things that can go wrong. Either 1) the alternator isn't putting out enough (or nothing at all), 2) the alternator is putting out too much, or 3) the battery is not accepting the voltage that the alternator is producing.

Hope this helps.