erratic dash gauges

the dash gauges on our 1986 K2500 has some very erratic gauges, going all over the place then settle down and then start pinging around again, I have check the ground and it is good. Is the some sore of resistor in this as I don't see one when removing the gauge cluster?

check your grounds and do a back probe would be a good start and fuses

I agree will this

check your grounds and do a back probe would be a good start and fuses

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or a gound that is not makeing contact all the time so it loose good some times.(bumps in the road, closeing the door, engine rev or idle, shifting in gear or out of gear.)