I followed these steps. My tach was stuck at 5k. Turns out the rubber inside the gauge shrinks, and stops the needle from moving. I pryed the gauge open slowly, peeling back the bezel until I could remove it and glass off the gauge. Lifted out white rubber inside gauge. Needle moved freely. Discarded rubber, reinstalled glass and bezel. Plugged back in, works perfectly. All left is to deal with clear silicone.
http://greenhulk.net/forums/showthread.php?t=206298
http://greenhulk.net/forums/showthread.php?t=206298
