dash guage ground

[Joe400]

does anyone know where the ground is for the temp, oil pressure and voltage guages? its a 93 ranger supercab and the temp guage as well as the oil pressure slowly go up until they are pegged past the max mark. i know its an electrical problem because i tested both of them with mechanical guages and every once in a while they'll be perfectly normal. also, the voltage guage reads below normal most of the time, even though the alternator and battery read 12 - 13 volts. it sounds like a loose ground to me, but who knows.


thanks,
joe