I have a 1987 Mazda rx7 non turbo and I have a problem with the dash guages I have checked fuses and all are good also the battery voltage does work only when I tap the top of dash idk what it could be any suggestions would help please

 

sounds like a bad connection at the back of the cluster.

 

Cool will check it out

 

Do the turn signal lights in the dash always work? If they suffer the same problem as your gauges then the ground is possibly the problem.

 

The turn signals do work the spedo and odometer counts and speed works I notice the warning lights were the clock is turns off and on sometimes once I hit a bumb just the temp rpm and oil pressure don't work battery works once I tap the dash board

 

the speedo is mechanical so it is not tied into the electrical system at all (well,really only the lights that illuminate it).It is cable driven from transmission to the cluster(gauge).
banging on the dash,to me,indicates a loose connection so you will have to disassemble the dash to get at it,simple as that.

 

Nice will get on it asap and see what I can find and thanks for the info it points me in the right direction