Battery Light Problem

[nick-A6]

Last night while out for a drive, the battery light came on and the volt guage slowly very slowly started to drop. pulled over switched it off checked everything. A side light had gone ?

Restarted it same problem, then the car went into limb home mode as the battery volts dropped. Found out if i rev the car to near the red line everything works fine and hunky dorey for the rest of my journey!!!

its a S reg 2.5 V6 TDI A6

any answer's please fellas

Cheers
nick

 

[enda1]

It sounds like your altenator is no longer charging the battery. This could be because there is a fault in the altenator itself or a loose connection. The drive belt to the altenator could be a problem and is slipping, but you owuld hear this and this belt also drives your power steering pump and water pump so if you have no problem here then its unlikely to be the belt.
It could be a short to earth but if the battery is draining that quickly then the current would be quite large and you would expect the fuse on the circuit to pop to protect the electrics.
Start with the altenator

 

[enda1]

The other thing it could be is that the glow plugs aren't turning off when they should be and this wolud be a huge drain on the battery