If you hook up the electric (AC) heater directly to a 110 volt source,
have the fridge dead level and have no problems with the ventilation
of the fridge compartment then your system should cool. If you get NO,
or poor cooling you either have a defective heater element, a heater
element not correctly seated to the cooling unit or a defective
cooling unit.  When you say "quit working" do you mean you had no
control panel function or simply no cooling?? By the way, leakage
usually leaves behind a yellowish looking residue on componets of the
cooling unit.  Circuit boards do go, but look first for other issues
first.

Bill, RVIA Certified Tech