I have a 2006 5-speed Jetta TDI. When the air conditioning is on all the way and I am downshifting at a low rpm the car shuts off. The clutch has to be all the way in, and the AC all the way up. The red battery light pops up on the dash, and the car is dead, whether at a stop light, or more recently, in a busy merge lane. This isn't consistent by any means, but tends to happen at the most unexpected moments, and never when I have a mechanic from the shop riding along (Of course). My car has been in and out of the shop for a while, but as the problem 'cannot be duplicated' it is not being diagnosed. The car isn't spitting error codes, and doesn't do this when the AC is off, but it is still a huge problem. I'm stumped, and so are the technicians. Has anyone seen anything like this before?
I know it sounds like a weird problem, but the car isn't stalling. The transition from engine turned on to engine turned off is completely smooth and one barely every notices until the car doesn't go forwards when you hit the gas pedal again.