My truck camper was a 2001. To run off gas, it had to be switched to gas mode, then you had to push and hold a button that allowed gas to go to the pilot, then you pushed an igniter button a bunch of times. There was a meter with a needle that would move from the left side to the right, ( green), and then you can let the gas button go. At that point the pilot is lit and the gas thermocouple allowed the pilot to stay lit. If you have that little meter with the needle that is how to do it. I don't remember the brand for sure, but I think it was a Dometic.
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