Honda Civic Charging Problems

I have a 2002 Honda Civic EX that is having problems charging. When the car is idling, the voltage is around 14.5, but when the car is revving, it drops down to 12. Over the period of a few days, depending on how it’s driven, the battery can be almost completely drained. What could cause this, or am I barking up the wrong tree?

Your situation is almost completly backwards from what it should be.My experience has tought me to start my diagnosis of any electrical concern at the beginning,the battery.

The battery is two years old. I charged it today, so I’m going to check that it’s holding a charge in the morning.

Actualy, this is hopefully near the end of a long saga. Last week it had problems starting, and then soon after that the ABS light started coming on and the dashboard gauges would drop to zero whenever I used the AC while accelerating. The car still ran fine, however, and the dashboard problems don’t happen when I’m in neutral. I took it to my normal shop, and they checked the codes. The only ones that showed up were a fuel/air sensor and the knock sensor. After they cleared the codes, the car refused to start (All lights come on and starter solenoid clicks, but starter won’t engage.). A $200 visit to the dealership fixed the starting problem (apparently there was an old aftermarket alarm system installed that was causing the starting issue) but they broke the turn signals (they don’t click or blink). They swear that they didn’t brak the turn signals, so I’m taking it back to my shop for diagnosis. In the mean time, the dashboard weirdness came back 2-3 days after it came home from the shop. I think that problem relates to low voltage, which is why I’m trying to test the charging system. I would expect the voltage at the battery to be around 14 - 14.5 when idling and when accelerating with no additional load on the battery. Am I wrong on that count? I’m also going to have the battery checked out tomorrow regardless of its condition in the morning just to be sure.

I disagree. Have the alternator checked. The voltage should not drop, and it is the alternator that puts it above 12V. If the voltage drops to 12V, then the battery is draining to maintain the 12V. The alternator can be checked before replacing at most parts stores.