The heater master power switch. I've added warning labels advising operators to not shut off the master power until the unit completes its cool-down cycle (Google melted diesel cab heater fans if you want to see what happens if you don't do this).
The switch is mounted on the side of the board I wired to run warning lights and other added accessories. The cab heater was added after all the warning lights and other aftermarket items were installed.
Also visible is a CO detector. It's actually showing some CO as I had just started my truck outside the garage as it was parked backed in with the tail pipes dumping into the garage, so I know they work. They alarm at 50ppm.
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