There is a good chance that the ground wire to the trailer is only 12#. You need at least 10# to get enough power to the fridge
Guy who did the install on my RAV4 had to go buy 10# wire as it's not normally used.
Then, I scrapped the idea of running the fridge
on 12V because, it was pointed out to me, that if the trailer battery
is depleted and you travel with the fridge
on DC, the trailer battery
will still be depleted when you arrive at the next camp. Fridge will use all the power the tow delivered ( and maybe more ).
Don't forget to shut off the fridge if you stop for lunch.