2002 diplomat monaca moter home all lights work except the ones on the lower side of the side mirrors

See You Tube Video tell all;
https://youtu.be/4G8TjuZfyHE

Depending on the specific year of your coach, it will be under the hood, front left side or driver side kick panel (by the pedals). Should be black plastic and it will have a diagram printed or stamped under the lid to identify the specific fuses you are looking for.

On almost all trailers, the wires coming from the vehicle plug are wired directly to the lights on the trailer without any fuses inbetween. This means that, if your blinker and brake light on the left side is not working, either the bulb is burned out, you have a wiring issue, or corrosion in the vehicle plug or bulb socket is preventing voltage from reaching the bulb.

The light switch for the LED's on the front is under the 5th wheel area on the left / drivers side. The light switch for the LED strip on the lower r/h side is in the storage area right side and is a little black knob where the TV connection is.

Did you check the obvious like blown fuses and dead bulbs? Corrosion in the sockets? RVs do eat bulbs!!!! Replace with LEDs. Expensive, but will be the last time you ever replace it.

First, turn off AC, refrigerator, all lights, water heater, and pump.

any of those will draw current and make sparks when connecting the terminal on the battery.

check the amount of current draw with an ampmeter.

use an ohmmeter to check the wire to ground - without connecting the battery to see if there really is a dead short to ground.

If you don't really understand above, then: get to a RV repair place that is familiar with winnebago older models.

good luck.

Most likely:
If it is a regular rhythm, look at your converter. The converter changes 120vac to 12vdc. Your interior light are 12v. A failing converter will cycle like that. Probably in the diode array and not servicable. I recommend one of the multi-stage converters. More $$$ but worth it. An alternator (on the engine) can do the same thing if the engine was running.

If irregular, it is varying loads on the power feed. Not much you can do about it except change where you hook up.

What is a "moter"?

If anything else that is battery operated works, it might not be the converter...