I would check the multipin connector that connects to the back of the panel. Could be that one of the pins is corroded or sprung open. I would also check to see if the connector has power so you can determine if the problem is upstream or downstream. I don't have access to the pin layout in the connector perhaps someone can direct you to it. It can't hurt to check the grounds bolted to the chassis behind the panel.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)