A/C Repair

John had a small, window A/C unit. Somehow it got dropped and it quit working, so I said I would take a look at it. I think that was about three months ago. I know what you're thinking, it got dropped and if it's not working anymore, something inside must have gotten busted. The odd thing was, there was no visible damage on the outside. It must not have fallen very far or very hard. Maybe some little plastic do-dad got busted and we can glue it back together. So a few days ago I opened it up and discovered what was wrong with it. It was blindingly obvious, the power cable had gotten ripped from it's connections and the ends were just flopping around in the air. Okay, this should be an easy fix, just plug the connectors back onto the spade lugs protruding from the switch body, except, one of the spade lugs has broken off. The other is bent, but this one has been broken off. You can see the jagged end of the broken off spade just protruding from the switch body. I look in the connectors on the end of the power cord and find nothing. I pick up the whole unit and give it a shake. Nothing falls out and there is nothing loose rattling around inside. Well, A/C units are full of holes, maybe it was ejected at the time of impact.

Right then I had two clues as what happened, but I ignored them both. Then I noticed that one of the power leads was much longer than the other, and the nylon clamp that had been holding the cord had been ripped apart. This was a fairly stout clamp, it was just a nylon strap, but it was secured by two screws. This is another clue.

I ignore the clues and press on with my instinctive solution - making a connection to the switch where that tab broke off. Osmony suggested soldering a piece of metal on there, he end cut a piece of metal to use, but I'm not that confident about my soldering skills, trying to solder two dissimilar pieces of metal, soldering for strength, not just to make an electrical connection, and having to solder right up next to the plastic, all that dissuaded me from that approach. It might have been possible to disassemble the switch further, but that would have meant making diagrams of how it fits together. So no, I'm not going to try and solder it.

I've already opened the switch. I can see a nice, big flat piece of metal about the size of your fingernail that I can drill a hole in, and look at this I have a screw just the right size lying here along with a standoff! Perfect!

Inside of switch with new screw and standoff

So I measure and mark and drill a hole in the top of the plastic case. That exposes the metal plate through which I now drill a tiny hole. Next is the tap, because the screw I picked up is a machine screw, not one of them ignorant sheet metal screws. Coincidentally, I have a box of small taps and one of them appears to be just the right size. I think it's a #3-48. Did I tell you about this box? I probably should. It's an alligator wrapped case about three inches square and one inch tall with a lid  with a snap. It was originally made to hold microscope slides, there are pieces of wood attached to two sides of the inside of the box, cut with grooves to hold the slides. I don't know where it came from, but when I came across it I thought it was just the right size for holding this collection of taps. The taps I picked up a my first job. That was over 50 years ago, and I'm still carrying this little box around with me.

I reassemble the switch, connect up the wires, mount it in the box and, are you ready?, plug it in, and bang! The circuit breaker trips immediately. What happened?

Disassemble the whole kit and kaboodle and lookie here - the piece of metal I drilled and tapped for the screw, that piece goes clear across the top of the switch and forms the lug for one of the power lines. By connecting the other power line to the screw I created a very short circuit. No wonder the circuit breaker tripped. Could have avoided this if I had looked a little closer. None so blind as he who will not see. I knew what the problem was, I didn't need to look at nuttin'.

John's window A/C switch showing broken tab

Now I realize the long power line goes to this capacitor looking thing mounted at the top of the unit. That explains why that lead was so much longer. It also explains why I didn't find a broken tab floating around loose. And the broken tab? It was a suspiciously clean break, almost like it had been cut. At the factory. When they made this machine. Bah.

Reconnected the wires to their correct connector tabs, plugged it in and it runs. Well, the fan runs, but turn the thermostat down until the compressor kicks on and all you get is some ugly buzzy-screechy sound. So not fixed. Osmany brought the VOM home last night, but wouldn't hand it over until he staged his little 'oh dear me, I forgot to bring it home' pity party. The dog.

Maybe today I'll discover what the new problem is.