High water temp gauge: Bad dash ground
My consistently high reading water temp gauge (on my 2000 Country Coach Magna) was due to the dashboard gauges not being properly grounded. I ran a new ground wire from a point on the front frame area (situated nearby the HVAC unit on the passenger side, behind the dash access panel directly in front of the passenger seat) to the dash gauges. The dash gauges all have a common ground wire and I simply tied into the that existing green wire from my new wire run. Preseto! My consistently high reading water temp gauge returned to a normal running temp of right around 200 degrees. Similarly my consistently low reading volt gauge (showed around 11 volts) ran higher at just over 12 volts while running down the road.
Tim Sullivan, 2000 Country Coach Magna, C10 Cat with 2015 Toyota Prius toad.