Need spme help finding..............

[Darek78]

hi guy's i need finding the ground wire for the gauge cluster
i have a wierd problem with my gauge's the temp is all the way past the red point on H my volts are up to O in normal my oil pressure is past H mark
at night it was raining and in the morning when i started the car all the gauges show'd everything the way it should my temp was at R and M in normal and oil pressure was in the right place to and my volts also
and later doing the day when was time to go home everything was miss leading again temp high oil up volts down i'm going nuts with it
Alt is good chargeing fine
my battery is Yellow OPTIMA
any ideas????????

Thanks Derek.N