Where did you get the STP filter, BIG LOTS! LOL
Being an electric gauge, check your electrical connections.
From experience, I never use crimp connections on any thing but temporary connections, they do deteriorate. And with a gauge that works off either voltage or resistance, or voltage controlled by varied resistance. Re crimp new terminal ends or solder them.
It did sit a while.
I need a rev limiter, too many 8-9k motors in my past to control myself.
