I have a 05 Mk5 Golf TDI. I have to jump it in the mornings as its battery is dead, but it will last all day if I'm driving it. It will start straight up if I stop for a hour or more, but if left over night it will be dead again in the morning. Also, the brake lights come on of their own in the early hours of the morning unless I go out to the car and pump the brake peddle. Any idea what might be causing these things to happen?
The Mk5 has a Central Control Module (I also saw it was called a Central Convenience Module). The CCM controls the brake lights, as well as many other things. If the brakes lights are coming on weirdly of their own accord, it's probably due to the CCM. I believe the only way to fix it is to replace it, which seems to have happened to many Golf owners. I believe the CCM is located under the dash above the pedal assembly:
Before changing any expensive parts on the Golf, check the brake light switches, very carefully. There are two switches on the vehicle activated by the brake pedal. Whilst the Golf is a very good example of European vehicle manufacture, its brake light switches could be thought of as flimsy. They do miss behave and fail, producing various side effects.