I have an air conditioner sitting on a window sill. Just lately, when it’s running, it shuts down by itself, and the electric cord gets hot. Last night, it shut down again, and I could see black marks at the end of the electric cord and the wall outlet. Looks like it’s been burned. Can someone tell me what’s wrong with my air conditioner?

There is a resistance connection at the outlet. Probably caused by corrosion in the connection. You will probably have to replace the plug and the outlet. If not, you could be looking at a fire hazard.

That’s pretty common with the type of outlets that are the type that the wire is just pushed in for the wire connection to the outlet. It could be that the tension on the plug prong from the outlet isn’t as snug as it once was too. If the tension gets loose, arcing will occur as the load gets heavier and the contact points get hotter. The more it arcs the worse it will get. Make sure nothing flammable is anywhere near it.
If you replace the outlet get an outlet that’s rated for 20A. Look for one that either clamps the wire in place or you have to curl the wire around the screw. Those give a much better connection than the push in type. Watch out for the prong style on 20A outlets. There are some that use a horizontal prong and a vertical prong. Look for an outlet where one prong cutout is both horizontal and vertical. Those will allow the use of a 15A plug and a 20A plug. If you don’t understand electricity, its time to call an electrician. It is the outlet that’s the problem. Your air conditioner is probably near the amperage limit of the outlet. Typical outlets have a 15A limit.

You solved my problem. I went out and bought a 20A outlet and installed it. I don’t feel any heat anymore from the outlet or from the extension cord when I run the A/C. I could not believe my eyes when I took out the old outlet. It was burned to the ground. Good thing I replaced it just in time.

I see that at work a lot. It was something I’ve dealt with recently. Sometimes even a 20A outlet will fail too. It all depends on how it’s treated when it’s in use. Wiggle the cord or put a strain on it when there’s a heavy load and you’ll initiate arcing. That will start the failure process again.

He can replace the outlet with a 20A outlet, but if the wire running back to the breaker box is still 14/2, he can’t really place a 20A breaker in the panel and not have any problems. He would need to pull 12/2 wire to handle the extra load. Yes, the reason the cord is hot is because of the draw on the underrated wire. If the cord is blackened, DO NOT USE IT! If you do, you could end up causing an electrical fire! While I can understand the desire to cool off and take the chance, you might end up regretting it later.

I see it all the time where there’s a 15A outlet and a 20A breaker, I think they use the 15A outlets because they’re cheaper. I doubt the wiring is 14 gauge. That’s usually only used for lighting. I never mentioned changing the breaker. Using heavier parts after the breaker won’t hurt a thing. The weak point is the contact points in the outlet. If they’re carbonized and corroded by arcing they’ll decompose fast if they are kept in use.

The important thing here is to find out what gauge wire is running to the outlet before changing to a 20 amp type. 14 gauge goes with 15 amp. 12 gauge goes with 20 amp. BEFORE MESSING WITH THE OUTLET MAKE SURE THERE IS NO POWER TO IT BY EITHER TURNING OFF THE CURCUIT BREAKER OR PULLING THE FUSE. 110 doesn’t usually kill but sometimes it does. And either way it smarts. If you can pull out the wire from behind the plug enough to see the markings on covering on the outside of the wires there will be something stamped on the covering. It will look like 14/2 or 12/2 with some other info. You might have to dirty your finger and rub over it to read it. Some people leave enough wire in the gang box (the box behind the wall that the plug screws into) to pull out some don’t. I like to leave enough extra to be able to pull the outlet out enough to easily replace outlet if needed. Some cut the wire so short you can barely pull the outlet out enough to get to the screws holding the wires.

You can also go down to your main circuit breaker box and see what type of circuit breaker or fuse they used on the circuit. I’ve never known an electrician to put a lower rating breaker on the circuit breaker end of the line than the wire will handle. But they do occasionally use the lower rated outlets on the outlet end. OH And I almost forgot the most obvious thing. Check the rating on the A/C unit. Most window units these days are rated at 15 amp but there are still some heavy units rated at 20 or more. And if you use an extension cord. (NOT A GOOD IDEA WITH A/C UNITS) use one heavy enough to carry the load. If this is too much info for you then check with your friends to see if they understand electricity or hire an electrician. Better safe than sorry.