When it comes to constant car maintenance the Passat doesn't disappoint. I took a drive this morning to our local garden supply store and on the way noticed a "battery" warning light. After a quick diagnostic with my multi-meter and Volkswagen scan software I determined that the generator was bad.

So how did I figure it out? For starters I measured the voltage across the battery connections while the car was running. The reading was 11.8 volts which is well below the 14+ volts you'd expected with a functional generator. I turned off the car and measured again, this time I read 12.3 volts. A bit low but not out of whack. I then let the battery sit for an hour or so and rechecked, this time reading 12.4.

What happened: The battery was discharging (or draining) while I ran the car. The alternator/generator was not recharging the battery so it was losing power every time I started or drove the car. When I turned the car off the battery went back into "recovery" mode and the voltage creped back up as the battery regulated its self.

Eventually the battery would have died or become too weak to start the car. I made a quick trip to the store and bought a battery charger, which will keep the battery well charged until the replacement generator I ordered arrives. The temporarily solution is to recharge the battery every night so I can drive the car, though I'll have to do it without the headlights or over very long distances.