"Tim S" wrote in message
...
"Ron Lowe" ronATlowe-famlyDOTmeDOTukSPURIOUS coughed up some
electrons
that declared:

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.

That's been my experience.

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. )

15.5V seems high. 14V-14.5V would be more like the sort of voltages
I've
been used to seeing with the alternator going flat out *and* the
battery
fully charged *at the battery terminals* (lower at the load
terminals, due
to drop in the wiring).

Thing is, 15.5V I reckon will damage the battery - and if the
battery is not
fully charged, it should be holding the vehicle general supply
voltage down
to something more sane**

** Meaning the alternator might produce a high-ish output voltage in
order
to drive lots of amps into the battery via it's connecting leads,
but the
voltage at the battery terminals shouldn't actually get that high, I
wouldn't have thought.

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

Do they still use "Lucas, Prince of Darkness" electrics?

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.

I would challenge it's operation to the dealer.

It seems too high by a good volt - my old Daewoo, I think, used one
spare
bulb in it's whole time I had it (8 years) and that was the interior
light.
Maybe it had a new headlamp bulb too - certainly nothing else.

Cheers

Tim

To get more evidence, get the specifics (make / model) of the battery
and get the tech spec from the manufactures web site re max voltage
for charging. If it's being exceeded then thump Landrover !

AWEM