An update from the original poster.
A suggestion from an electronics technician friend was to cover the back of the instrument panel (the actual circuit card, AKA PCB) with a conformal spray-on coating, which protects electronic components against moisture and dust and other environmental...
I didn’t think of heat from engine, so I measured the distance from the panel to engine. It’s ~10”. There is a thick metal panel various body panels bolt to between the engine and the fuel tank, and a large air gap over the fuel tank and under the cowling the instrument panel fits in to. Under...
Pictures added to original post.
The foam padding/layer is not glued in place, except for possibly a few spots. Functionally, it appears to keep the solder connections covered and provide a seal for the bulbs.
Greetings
I own (bought new) a 2001 New Holland TC29D. Red squirrels built a nest behind the instrument panel. They chewed a few wires going to the panel and the fuel sending unit, and the foam padding on the back of the panel. I spliced the wires and so far everything is working as it should...