[51woodie]

Phil. Best thing to do is get your volt meter and start checking various connections to determine if the problem is the light switch. Assuming your Merc is similar/same as my 46 Ford, and the light switch is the same, there is a small slot (see pic) on the top of the switch on the dash side of the connections where you need to insert a small screw driver to release the switch pull. Push the release back towards the connections, turn the knob to the right 90 deg. then pull on the knob. It should come out. It is a challenge as it is in a tight spot and mostly done by feel. Once the pull is out, a small pair of needle nose pliers can be used to catch the notches in the switch mounting nut to remove it. The switch can then be lowered below the dash to do testing. I included some wiring diagrams in case you dont have them. If not clear, send me a PM with our email and I can send you the documents via email.