1999 Jetta perpetually low battery

Now, the battery tests at 8.75V, it is a new battery. (the alternator is working fine, tested).

Get the car running, it will run fine and battery will charge. Let the thing sit overnight, temperatures 50-60 degrees, and it will read in that 8.75V range.

Getting frustrated trying to track down what is eating the electricity when the car sleeps.

Please help.

It is probably a short. You could do a continuity test on each circuit. Or try pulling a fuse at a time overnight to pinpoint the bad circuit, and take it from there a wire at a time. Get your hands on a schematic.

Not a VW specialist,but you appear to have a current drain with the key and engine off.A continuity test will not help. You will need a multimeter with a 0 to 10 amp scale and a milliamp scale,MA scale over 500 Ma. Normal amp drain on a modern car is app. 250Ma. Disconnect the pos. bat. cable,set your meter to the 10 amp scale and check the draw.If you see a 0 drain the 10 amp scale,set the meter to Ma and recheck. With the battery going to under 9V overnight I would suspect a heavy drain.Do some diagnostics if you do your own work,feel free to PM me if you want to.If you have any after market amps,etc. I would look there first.