An additional entry for your known problems list.

I have a 1990 G60 which has drained the battery when

parked since day one. What I eventually discovered

is that there is a power window relay control unit

mounted to the left of the left rear passenger seat

which has a connection to the door switches (why?).

I observed that when the unit is first connected with

the doors CLOSED there is no power drain. However, as

soon as a door is opened a relay engages inside the

unit (you can hear it click in) and from then on there

is a consistent 100mA drain on the battery. You can

only release the relay (and the power drain) by

unplugging the power feed to the relay module. This

power drain is not a problem if the car is driven

regularly, but if you only use the car from time to

time you'll be fighting a dead battery more often

than not.

My quick fix to this problem was to disconnect the

wires which go to the door switches. Every thing

appears to work fine without this connection. A

"smoking gun" is that the door switches were changed

in 1991 so that there are isolated contacts feeding

this control unit instead of the 1990 version which

shares the switch with the overhead light unit...