Left signal effects instrument panel… tach, speedo, gas gauge (needles bounce with blinks) ???
That is not a question no matter how many question marks you use.
Likely an issue of a bad ground.
IIRC, that was just one of the many electrical issues with my POS Volvo, and the ongoing issues were almost always the result of bad ground connections.
If you search web forums that specialize in these types of trucks, you’ll find lots of older dashes conking out. This could be your problem here.
But like others said, check grounds. Also check battery cables for clean/tightness, and make sure your alternator is working within specs.