Does your 21EC have an actual temperature guage? I have the last 2006 21 built before they changed to the EC and mine does not have a guage. It only has the alarm, which is sensitive. A couple of time the water strainer became partially blocked and the alarm sounded at once. I have considered adding a guage because I have always had a concern with idiot lights and alarms only. Want to see a number even though the signal comes from the same place. Just feel when a number does not look right you check more than waiting on a signal that may not be working.
Ron