No idea if it is proper procedure, but I saw somewhere while reading up on these fridges, that you can sort of reset the ammonia by laying the fridge on its side. Perhaps Doug can advise on that.
I found the instructions for my 7401L on line; perhaps there is trouble shooting info there for your fridge too.
The other way to to run the fridge while driving is use an inverter to operate it on AC. That is if as it appears you don't want to leave it running on propane ( except when at a gas station or on a ferry of course)
Mr Wizard is right about the Dometic 7401L at least---the instructions say the 12v element wires must be so the 12v can only operate when the vehicle's ignition is on. The electronics 12v has its own set of wires to be permanently connected to the rig's 12v (with a 2a fuse)
