window unit air conditioner and wiring problem?

It seems that the receptical your A/C is plugged into is fed thru the recep. thats sparking. Turn off all power, and check for no power. Remove the problem recep. and see if the wires to it are pushed into the holes on the back of it. If so thats a voilation, you cant use the tabs on a recep. to feed thru, you must pigtail the hots(and neutrals) then attach the single wire to the recep.in case you don't know what I mean about the tabs, if you look at a duplex recep. you'll notice the top and bottom "plug" are connected together with a small piece of brass on the side, this is if you want to switch half while the other half is constantly hot, or for a dish washer/garbage disposal set up, or two different circuits. You are supposed to remove the tab for that kind of application, but you can't feed another recep. down stream from it, thru the tab. And the neutrals have to be pigtailed anyway, because the grounded(neutral) conducter must stay connected if a device is removed(safety reasons).

P.S. even window unit A/C's should be on their own circuit, and never use an extension cord on an A/C.

If your system has fuses it is very old, and the fuse should have blown long before the receptacle melted. You may have a fuse which is rated for more amps than the circuit can handle, for example a 30 amp fuse on a 15 amp circuit. You can check the size(gauge) of the wire with a tool purchased from your hardware store. A 14 guage wire for 15 amps and a 12 guage wire for 20 amps. You can find out which circuit has the least load on it by pulling the fuses and seeing which electrical devises turn off, them move the ac to the one with the least load.

Theres no problem about your AC, the problem is your Convinient Outlet (CO) was connected allso across the rooms CO and there's a loose connection happened to that CO going to main switch. The best solution to your problem is to install a separate line going to your main switch. Thats the standard and safety measures required by the local city engineers office. Install a AC outlet accessible to AC power supply cord and then install a 30 amp. breaker then lay-out electrical wiring going to the main breaker and you can connect it before or after the load-side.

change the wire. the gage of the wire is too small and is pulling to many amps. change the wire size or run a dedicated circuit to the unit.

maybe all your out-lets are on the same circuit as your ac unit. the ac needs to be on its own fuse. the wiring might be very old or bad.

its sounds your wiring isnt up to par the a/c is a 110 volt window shaker you may have to many outlets on one circut breaker or fuse

lose wire across the room turn power off ,put a new receptacle ,and tied good

buy a circuit breaker plug extension for the a/c to be plugged into......10,000btus is usually the limit, old wiring will blow at this or greater