Battery is going dead, but alternator checks OK

[davidfriend]

I replaced the battery in my Q about 2 months ago, it had started cranking slowly, then one day I drove about 3 hours and when I got there I stopped and filled up at a gas station and when I tried to leave the battery was completely dead. I got a jump and then went right to an autozone and had the battery replaced. It has been fine up until this last week when I left the car sitting for a week while on vacation. When I came back from vacation, it was completely dead. I jumped it and it started fine, but it didn't recharge even after letting the car run for a while. I jumped it again and took it to my auto shop, the diagnosed that the terminals were bad and not providing a good connection, they replaced the terminals and charged the battery for an hour and it was working fine. I picked up the car to leave and it barely started, then when I stopped to get gas a few minutes later it wouldn't restart at all...

So when I get the car jump started it works fine, so I can't see that the alternator is having problems, but its either not charging the battery, or there is something draining power from the battery (hence why it would have gone dead sitting for a week, when before that I was driving it everyday w/o a problem)

any ideas?

[Infinitiguy19]

The alternator on a Q45 was never designed to recharge a dead car battery. All you end up doing by forcing the alternator to charge the battery is kill it.

I would never go back to the shop you went to because clearly they are incompetent. After all I have been through I am very scared to leave my Q in anyones hands I don't trust.

I say have the alternator load tested and see what happens. My guess is you need a new one from all the stress of charging the battery so many times. Then check for a relay sticking open.

[masshead87]

This same problem caused me to have to sell my last car/girlfriend, and I would give anything to know then what I know now.

Parasitic power draw: like Infinitiguy19 said, either a relay sticking open, a switch stuck in the "on" position, or a frayed wire coming in contact with bare metal.

Shops would rather sell you new alternators because they are expensive and they'd rather make money on that than fool around with an amp-meter and find out where the draw is coming from. This is unfortunately a job which you, or a car buddy, need to do yourself to avoid getting buttraped any further.

I know Q45.org has a section on power draws, on my last car I learned (too late) that you had to manually check every relay point with a meter to see where the draw is. It's a pain in the a** job but that's the only way this is going to be fixed. Good luck, and don't give up. And don't feel too bad: I wound up buying two new alternators before both of my "buddy" mechanics decided they didn't want to work on it anymore. Had to sell it since school was starting the next week. *Sob*

[Q451990]

What is the voltage at the battery terminals while the car is idling, and off?

Heath