Might you have two or more screws on the bottom of the door that you say can't be opened? That is not uncommon. And when you do gain access, take a look at the SeeLevel system for monitoring your tanks. They have a pretty good design that will give you fairly accurate information on your tank levels, and the installation is relatively uneventful.
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Jim & Angie, Boise, ID
2021 Entegra Esteem 27U
2017 GMC Acadia Denali
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