TravelTiger
Founding Texas-West Chapter Leaders-Retired
The older Marshall Automatic switchover valves had an accessory available to let you know INSIDE the trailer when a tank had run out and the valve had switched over. It was a clip-on electronic sensor that detected the red flag, and had the wiring to an alarm lamp, usually mounted in the trailer electrical control center.
http://www.modmyrv.com/2009/12/07/rv-propane-tank-changeover-indicator
We added this on our ElkRidge, loved it in the winter months! Especially when we could go through a 30# tank in 2.5-3 days. It flashes a little light inside when the tank switches from one to the other. That way you know you need to refill a tank in the next day or two.
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