87 740 turbo no power through ignition

parked the baby at night and in the morning no-go: Turn the key and no
power comes on at all (no lights, etc, not to mention the engine).
battery is fine and so are the fuses. can start her up using jumper
cables though, but as soon as I turn the ignition off the only way to
start her up again is through the cables. anything I can look at
before taking her to the mechanic's?

 

If it fires with a jump start but not with its own battery I would suspect
the battery has gone south. Have you got another battery to test this? Or
can you take the battery out and take it to a shop to test it? I know you
said the battery is fine, are the battery leads on tight, mebbe putting a
crocodile clip from the jump leads over them is causing a good contact?

Stuart.

 

I too would suspect the battery, but if there's a bad connection between
the battery and one of the big cable terminals, you could see this
problem as well. Jumper cables bypass this connection because you
connect them directly to the terminals. If you're doing the jump
starting as you're supposed to, connecting the negative cable to the
engine block, so your last connection is not made near the battery,
you're then bypassing the whole negative cable, so that could be suspect
too.