Hi, all.

I have a Land Rover Discovery 3 here ( still in warranty ).

The vehicle has a voracious appetite for light bulbs: I'm replacing tail /
brake lamps every couple of weeks, and the same with headlamps. And at
around a tenner a pop for the headlamps, I'm getting a bit fed up.

Also, the kid's DVD players ( after-market ) in the back seats have started
shutting down, usually when I start the engine.

Fault-finding the DVD players, I was checking for the presence of 12v at the
power cable.

I found it to be 15.6v with the engine running.
IMHO, that's too high, and possibly the cause of the lamp problem.

Bench testing the DVD players shows that they indeed shut down at around
15.5 v ( protection, I guess. )

What is reasonable maximum voltage on a vehicle 12v system with the engine
running?
I'd guess around 14v.

Googling this, I have seen people saying the disco uses some fancy automatic
system to optimise the charge voltage which takes into account all sorts of
things including vehicle electrical load at the time, and temperature ( the
battery is apparently temperature sensitive ), and possibly phases of the
moon.. This can apparently cause the charge voltage to vary up to 15.5v,
I've read. ( It's -9 degrees here at the moment, and the vehicle electrics
are often well loaded with heated windows and seats, wipers, fan blowers
etc. )

Am I seeing a fault ( voltage regulator on the alternator ), or is this just
within normal tollerances with these vehicles?

Is it reasonable for the thing to run at 15.5v, and chew up headlamps?
I don't think it is.
I'm looking for some opinions before I need to argue with Mr. Land Rover for
a warranty claim.

Otherwise, I need to put a 7912 regulator in the DVD player power lead!

--
Ron