87 d100 dash guages all screwy help please
 

ok so my 87 d100 is having some issues with the guage cluster. i cant seem to find a solution im hoping you guys can help. my guages work fine when the lights are off but when i turn them on the turn indicaters light up and thats it. also the guages all drop to zero or go all the way up except the amp guage. when i open the door with the lights turned on the dash lights come on if the knob is turned all the way up like it would be if the dome light is turned on but the temp gas and oil pressure guage are all at zero or there all the way up it just depends on what they feel like reading at the time. this is really confusing and startign to drive me nuts. im thinking maybe the light switch itself is bad or possibly a ground somewhere. i aslo remember reading somewhere about a voltage regulater type thing for the cluster could this be my problem or do i rember incorrectly. i hope someone can guide me in the right direction i really hate not having oil pressure and temp guage at night. thanks jeremy

also the hibeam light is on on the dash but only when the low beams are on. and tonight when i was leaving work i started it to let it warm up and everything was working as normal but then stopped again and left me with no gauges and and only the hibeam and turn signal arrows lit up.im beginning to think i have a loose ground or something is there any grounds around in or on the dash that may cause this? can someone please help it is greatly appreciated. thanks in advance jeremy