The manual says you need 1 inch space all around, sides and top. Also do not place near heat sources. Is this campers side in the sun?
I might measure it with my cheap digital (frig) thermometer. Tie it to a string and hang it back there.
It definitely needs ventilation to carry the heat away. Otherwise the temperature will keep rising until something gives or plateaus. There is likely a maximum temperature difference it can sustain, running full time.
Don't know if you can check 12v at frig. If not, I might add some small wires for my digital volt meter. Low voltage can cause overheating and high current too.
2017 Winnebago Minne 2201DS TT
2010 Chalet XL1930 A-Frame SOLD
Retired Engineering Technician