'83 Ram Gauges moving around a lot

I have noticed here lately that the gauges (temp, oil, and fuel) are
sometimes reading higher than normal. I have seen them sometimes jump to
the high side of the gauge then come back down to normal. The usual
readings are Temp: 3 marks from "C", Oil: 2-3 marks from "H" while
cruising. But lately the temp has been 3 marks from "H" and Oil is
almost full scale (right). My first thought is something is wrong with
the motor, but I have seen them all come down at the same time at the
same rate, which leads me to believe there is something wrong with the
gauge cluster. The fuel gauge also jumps about 3 marks when the other 2
are moving.

Can anyone point me in the right direction as to where to start looking?

Thanks for your help!!!

 

On that vintage of Mopar instrument cluster, the fuel, temp and oil
pressure guages are all fed from an instrument cluster voltage regulator
rather than from direct 12V power. The regulator nominally delivers 5
volts average, but the factory regulators are very crude thermal
switches that cycle about 2-3 times a second and depend on the slow
response of the guages to average out the voltage. Yours is sticking
occasionally. If you search the web for "instrument cluster voltage
regulator" you'll find several articles for replacing the thermal
regulator with a silicon voltage regulator from Radio Shack. Makes the
guages behave MUCH more accurately. Or if you prefer "plug and go," you
can get a replacement original-style voltage regulator from NAPA. Its a
little silver metal box somewhere on the back of the instrument cluster.
It plugs in with either 3 or 4 spade plugs.