Sounds like you are about to waste money.. IF IT WORKS on PROPANE than it (The Absorption cooling Unit. also known as the "Expensive part") Works
There are a few "Modules" involved in operation on electric and on gas.
1: The thermisistor (Temp sensor) Used in both modes. working
2: The 12 volt supply also used in both modes and working
3: The control board.. Now here we have a possible candidate (more on testing later)
4 A relay on said control board (Suspect but not very suspect(
5: A terminal board. may have a fuse. may be bottom dead center in the outside compartment.. More on this if you have a dometic.. The condensation drain hose is SUPPOSED to exit via a vent hole so it drip-drip-drips on the ground.. My Dealer said "OH we always put it out" but they did not.... TWICE... (I did) if they do not put it out it Drips Drips Drips on this board with anticipated results (Early board failure) .
Next and last we have the #1` Suspect the HEAT ELEMENT. On a dometic it's in a stack to the right. It has fabric coated wires leading to it.
Testing..
FIrst: Does the Control board sense AC. light the AC light YES Skip next sentence
NO: check to insure it is plugged in check to insure outlet it plugs into is good and last check that board I spoke of above.
NEXT.. Hook a volt meter and/or test lamp to the element leads
120 volt present:
YES: disconnect leads from element and measure resistance should be around 1/4 to 1/2 ohm as I recall (About 1/3 sounds right)
If open.. Replace element.
NO Voltage to element.. Control board or control board relay failure Contact Dinosaure Boards for a replaxement.