1992 tm questions

I bought a used 1992 tm and an dewinterizing and testing stuff before camping. I ran two small thin orange type extension cords from my garage to use 110 volt power. When I tried the air conditioner it would not run the compressor. when I when to a heavier cord it would cycle on and off quickly. Is this normal or is it low on freon? Does the camper have to be perfectly level for the frig. to operate? Does it have to have items in it to operate? Thanks for you help...I'm new to TM's. JOHN