Temp gauge acting NUTS

Temp gauge in my '94 Cherokee Sport acting crazy..When at idle (stop light) it "tries" to read normal temp...around 185 to 190...Soon as you give it gas it drops down to cold reading...I have changed out temp sensor on engine..I will be taking dash apart to look at gauge and wiring...I will meter out wiring...Is there anyway I can test gauge?...Thanks,Pete44

Check for frayed wires. I had the same problem with my Oil pressure gauge... I changed the sender unit, and it did'nt help. I started to pull the dash apart to remove the gauge and noticed a wire loom stuck in between the dash support brackets. Two of the wires inside were rubbed raw from countless hours of bouncing around. One of them was the wire from the sender unit. I respliced it and put a tie-wrap on the loom to move it up a little. No problems since. If you've got a continuity tester you can check for grounded wires without removing anything.