How to check the lights on instrument panel
 

I have an extra instrument panel for both my 83 W123 and 86 W124. Can I check all the bulbs in their sockets with a 12 volt battery, say a small drycell to use in the house in the winter time or could I even do it off the battery charger. Is there anything back of the panel that I would ruin if I probed it with 12 volts?

Yeah, if you know which connectors. I would recommend just jumping with a car battery though.
In those 2 cars, you can remove the rheostat for the dash lights and jump power and ground to the 2 connectors and the dash lights should light.
You can find the dimmer knob and look behind the cluster, the rheostat is made of a ceramic material, just remove the one screw and pull the rheostat off and you will see the 2 connectors for the rheostat.
Gilly