Not that good with cars but I am an electrical engineer:

Have you tried pulling all the fuses and reconnected them one by one to see
which one is causing the problem?  I note this has been recommended before.

Plan along similar lines:

1. List all fuses.
2. Each night pull one fuse.
3. Each morning check the battery.

Note which fuse was pulled when the battery is NOT drained next morning.
The problem will be on that circuit.

Pete

Hi,

I have to agree here, and it's a bit of a heavy trend now in automotive
market.
Former PSA's CEO thought nowadays cars are all technically equal each others
between brands - i.e the 406 worthes a Laguna, or a Mondeo, or whatever else
in the same market segment. And although being a good manager (when he came
at the top of PSA the group was merely producing 2M cars a year, when he
left they were a bit above 3 millions, improving benefits, and that's a goal
for every private company), I have to say I totally disagree with that.
He certainly gave too much of money to designers - I mean the guys with long
hair which are about to the look of a car, leading the tech department to
almost starve... When there was all of these electronics fault with 307s
(which was the first fully-muxed Pug ever), it sprung to eyes : nice ideas,
almost everything you could expect for electronics embeeding was there
(multiple ECUs and redundant buses divided by group of functions, useful
when failing). Some other makers seems they even didn't know about this
evidence...
But another thing came to mind : yes they were still a bit brilliant and
certainly a bit above most common cars (even if the "VW-style" in the 307
sounded at me like an alert), and they released another generation of pretty
good Diesel engines (HDI's) which common fails on early cars were due to
crap components provided by Bosch... But what's next ?
The 407 has an excellent chassis, at least front train, the rear axle being
took off a 406, *BUT* the Coupe has something too huge, hence a lack of
elegance, and I miss the 406 Coupe, which was eeer so elegant and somewhat
exciting, I guess.

Here we are : while Pug gave almost all of the design part to Pininfarina,
there were some ducks but the global stuff was great. Now the techs &
engineers have far less liberty, it misses something in the house*. I also
expect a great way back of engineering in its house. I well imagine an army
of techies and engineers coming on the design area, slapping some hippies
and screaming "get out of there !".

* To be honnest, they still manage to get some nice pieces of engineering...
For example the early 206 2L HDi Eco, able of giving 120g/km without heavy
modifications (instead of 138 in standard specs). I have one, it's well
driveable, and reports a better economy than the 205D I had before, although
being heavier, bigger, and more comfortable to drive.

Cheers,
--
G.T