So today I dug around under the driver's seat of my '79 300TD and found
what I assumed to be the connection for the switch for the buzzer that
sounds when the seatbelt isn't engaged. I disconnected the "harness"
(all two wires of it), and hallelujah, my seatbelt buzzer stopped
sounding when I turned the key to start the glow plugs.
Then I noticed that the front passenger window no longer worked. It had
been working earlier in the day. All other windows work fine from the
center console switches.
Are these systems in any way related? All of the fuses are intact
(despite me coming to realize that I might just as well replace them
all), so that's not the problem. I thought it very odd that
disconnecting the harness caused that problem to manifest, so I plugged
the harness back together, and still no window operation (but the buzzer
is back). Sigh.
Since I still need to diagnose the disfunctional vacuum I figure
tomorrow is as good a day as any to take the door panel off, but are
there any particular points of failure to look at that anyone can