Battery In Yaris Mk1 Keeps Going Flat

[eiriksmil]

My parents got a mk1 Verso, the Battery went bad and was replaced in 2007, fair enough after 7 years. Then it started getting harder to start again this autumn, my ma took it in for a 90k km service and told the guys to look at it.. What they did, they replaced a two year old Battery, which was a OEM Toyota unit actually. That held up for a month, now it's flat again... I'm thinking either the alternator, but I'd imagine the dudes at Toyota checked that out before they replaced the two year old Battery, or that something is draining power. Stock car, no amps or anything that could be on.. Any clues?

The car isn't driven much in the winter time, but my Benzo was left for the same amount of time as the Yaris was without a start and a new battery (2 weeks) and fired right up.

[BALIKBAYAN]

To find out if the alternator is charging the Battery you should meassure the voltage at the Battery when the engine is running.

You should have 2-3 more volts than with the car not running. You might also have a little bit higher rev than normal idling.