I'm experiencing loss of electrical power to my Mk5 Golf. It seems to happen mostly when the car hasn't been run for two or three days.
We changed the battery a few months ago. More recently, there was a loss of power and the car wouldn't start. We'd diagnosed it as the alternator, which was replaced. This worked fine for a week or so, but I'm now at the problem where I'm experiencing loss of electrical power - car sounds uncertain about starting, clock is reset etc. There's still some power, because the radio, lights and clock etc still operate, even if the car doesn't start.
The remote locking feature only half works, too. I can lock remotely, but I can't unlock remotely - I have to use the key. The fob has started to show a red light when the unlock button is pressed.
I'm assuming the electrical power is being lost somewhere else. I'd previously checked for doors not shutting properly or anything else I could think of that might leave a light on, but there was nothing to suggest that was happening.
So how might I start to diagnose how the car is losing electrical power? I'm completely stumped.