Strange Radio Short

[Edward Hamilton <hamilton@ptd.net>]

Here is a strange one.
The radio plays until I sit in the driver side seat, at which time it
shorts.  I've removed the seats, checked everything, to no availe.  Now,
in trying to isolate it, I find that if I press on the prop shaft hump
(just in front of the parking brake) it shorts.  I know there are no
wires under there, but I have raised the car and checked under it.  When
the car is in the raised position, a short no longer exists??

Regards,
Ed Hamilton