www.iFourWinns.com

Coming back from the beach later in the evening, so I turned on my nav lights + dash lights,and headed out. Look down at the engine temperature and it says 210
Slowed down and fiddled around a bit and I figured out that when I turned on my dash lights, the voltage (via dash meter) drops from 12V to 10V, which causes the funky high temp reading. Voila, turn off the dash lights = engine temp back to 170 as normal.
My dash volt meters really don't read correctly, they say 12V while underway and it should be more like 13.8 - 14.4V. But I expect the voltage drop was real enough and caused the temperature gauge to give an false reading?

Anyone seen this before and any ideas why this would happen?

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1969 Chris Craft Commander 47
1999 Four Winns 328 Vista - SOLD

More often then not, a bad ground to the panel. That one grond wire is used for everything on that panel. Just to rule it out. Run a ground wire from the battery or any other known good ground to the panel.