[beau1175]

I have read the posts about fixing a tach by turning the switch on the rear of the tach a dozen or so times, is the switch supposed to rotate 360 degrees or is it supposed to stop at the first and last number. Mine spins 360 degrees and is still stuck on 500 rpm as always.

[ColoradoDiablo]

Sounds like the switch itself is broke internally beau.
I have never tried rotating it 360 deg before , just back and forth between the three settings.
Time for a factory repair from Faria , or new gauge I'd say.
What style is your gauge package?
Can you shoot us a pic?

[beau1175]

I can take a pic and see if there is any info on the backside after work today

[Hudson River Steve]

I have an old Fariah tach that I removed from my boat sometime ago that had the same problem. I disassembled it and can tell you that there is nothing to prevent the switch from rotating a full 360 degrees, so spin away, you wont hurt anything.
If spinning the switch doesn't fix the problem then you may have the same problem as mine. What I found when I disassembled the tach was corrosion due to the way Faria assembles the unit. The brass studs that are used for electrical connections on the rear of the tach make connections with brass pads soldered to the pcb. Corrosion had set in between the head of these studs and the brass pads mounted to the pcb causing a high impedence connection, essentiall a bad ground.
Before removing the tach from your boat, try removing all the wires from the three rear studs marked Bat, GND & SIG. Then loosen the three brass nuts that hold the brass studs to the case about 1/2" to an 1", leave the unmarked stud/nut tight as it will hold the pcb in place. Try pushing the studs into the case and then pulling them back hard to break the corrosion coating. You will not be able to rotate the studs much as Faria molded in stops to the plastic. Retighten all the nuts and reconnect all the wires.
It's worth a shot before you send the tach back to Faria for repair or buy a new tach like I did.
Good luck!