1992 240 GL Weird Wiring Issues

[93Regina]

but have come up with no solutions

I would agree, and it appears your grounds are working just fine.

Reverse lights - Inspect transmission's connector, and use a jumper wire to activate, and see what happens to fuse #5.

Do report back...

[93Regina]

backup switch

Two wires - One is the hot wire from the fuse block, and the other wire feeds the backup lights.

So, it could be the wire at transmission and going to backup lights is shorting out if only fuse blows when reverse is selected.

So, follow the wire....or electrical-plug/sender at transmission is shorting out.

[93Regina]

I am still having problems with my headlights..... third is low beams, which doesn't work. Anyone have trouble with this?

The circuit has to be traced out: Volvo 240 1992.pdf (pg. 19, 22)

High beams are controlled via Step Relay

Low Beam circuit goes thru the Bulb Fail Sens

So, pull apart Bulb Fail Sens (driver side, up above brake/clutch pedals to the left) and see if power to headlight is there...

Understanding and Dealing with a Volvo Bulb Failure Sensor