NOOB questions sorry ahead of time. Fuel gauge and dome light
 

These Q's are for my 1982 265 D24 M46.
Ok this is my first volvo. I have 2 questions and searching really didn't help. My fuel gauge does not read past half (car has sat for 6 months prior to me purchasing it last Saturday. Are the gauges/senders the same for diesel and gas? What could be the culpret? 2nd I cleaned the contacts on both dome lights and they both turnon in 1 direction but only turn on sometimes regardless of the door open or closed in the other direction. They both turn off when switched in the center.
Thanks and I will probaly have many many more questions here in the very near future.

The fuel sender is the same as gas cars. it has two wires. You need to ground the positive wire to a known good ground. If the fuel gauge moves all the way to full then the sender or the ground wire to the sender is bad. Next just bridge the two wires together. I f the gauge moves to only half way with the wires touching then your ground has some excessive resistance. If you can't make the gauge go to full then the gauge is most likely the problem. You also might unplug the cluster and plug it back in to see if you can make a better connection.
Hope this helps