I'm no expert on RV fridges, but that doesn't sound right. I think it is the same coil for both gas and electric. The only difference between gas and electric is the heat source. Those with more knowledge will chime in soon. As to how long do they last. I had a truck camper that was 20 years old and the fridge would freeze beer.
2010 Rockwood 2604SS
2008 Silverado 1500 LTZ 4X4
Great Wife and Idiot Yorkie
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