I use a 2000W Coleman inverter in my RV to run the coffee maker and flat screen TV. I used to run a fat extension cord from the inverter in the utility compartment through an open window into the RV but decided to wire a 25-foot length of 14/2 Romex cable for a more permanent, clutter-free hookup. The cable goes through an opening under the bed and runs along the inside walls inside plastic cord covers. To facilitate pulling the Romex through the cord covers and around corners I stripped off its outer PVC jacket and paper separators. The run includes two duplex outlets. The new connection works for the most part. The coffee maker, power tools, a 19-inch flat screen TV, and a DVD player all work fine when I plug them in, but when I plug in the Toshiba 22-inch flat screen TV/DVD combo (even by itself) the inverter immediately cuts out and flashes its overload light. The crazy thing is that if I unplug the new wiring and run the old extension cord directly from the inverter to the TV then it works fine. The voltage level at the TV is 130V whether it gets there from the new cable or the old extension cord. When it runs with the old cord the TV only pulls about 55W with no startup surge. Can anyone explain what the heck is going on?
I would start by replacing the dodgy mains wiring with proper mains wiring
My first port of call would be to toss this whole wiring setup out and start over -- instead of cord cover, a proper, mains-power-listed surface raceway is the correct thing to use here, with individual stranded THHN wires run inside it. (NM cable wires are not designed for use outside the protection of a cable jacket, which makes it likely that there is wiring damage present that is contributing to the inverter cutting out.)
If that doesn't fix things...
If that does not solve the problem, I would get a power strip with a built-in noise filter and plug the culprit TV/DVD player into that instead of plugging it directly into a wall outlet -- this will help keep electrical noise from confusing the inverter.