Actually, if that's the big bundle of ground returns in the bottom of the cab that is one of the many ground mods that SHOULD be done. There are a number of others that should also be done, and ultimately you could be looking at replacing all of the connector pins to get everything working as it should.
As I've said many times over the years, Sys80 games are 79 more problems than Sys1 and both systems are an adventure! If you haven't already done so, I highly recommend you purchase the TOP DVD 'Black House Haunted Hole'.
D