What could be wrong with my A/C unit?

Question

I just installed a new compressor fan on my outdoor A/C unit. Before the fan went bad, it was working fine and had just had its annual service check (the service guy said the freon was fine, everything checked out, it was just really dirty). Now I get warm air in the house and the cold pipe is not cold, warm pipe is not warm. No clog in the drain, but also no condensation out of it at all. Just replaced the capacitor about 6 weeks ago as well, when that went bad.

My dad (not a pro, but a DIYer) says it is either low freon or bad compressor. Neither of us believes that all of that could have gone bad at once, however. Any suggestions on what to check? After $1600 in repair bills on our HVAC system over the last year, I have no money left to call an actual repairman out to fix this.

Answer 1

Check your start / run capacitors. They live in the outside unit, near the switch.

They look like oval or circular cans, and they feature prongs on one end and a flat bottom on the other. If either end looks even remotely non-flat, the capacitor has failed and the compressor won't run (even if there's freon in the line and the compressor is functional). Sometimes there is only one capacitor, as it has both the "start" capacitor and the "run" capacitor built into the same package.

If you are in doubt as to the "flatness" of the package, pull the disconnect near the outside unit, provide a bit of time to let the capacitors drain (10 min should be sufficent) and pull the capacitors out of the system (take care to identify the wiring, wiring a capacitor backwards is not recommended). Then find a nice flat table and if one wobbles, it is gone. If it is flat on the table, you dont't have this problem.

The repair (if needed) is a new capacitor ($10 to $15 at an AC parts supplier, no license needed for this part). If you find these capacitors failing more often than "once in a blue moon" it is a strong indication that something else is wrong with the system, like worn windings on the compressor motor, or possibly an electrical short elsewhere.

You can replace a two-in-one capacitor with two single capacitors (provided they match the original ratings) and vice-versa. But there's no need to get all fancy.

And everyone says "low freon" or a compressor. Get used to it. Occasionally they are right, but a failure like that sounds odd if recent repair work was done, unless the repairman did a shoddy job.

Answer 2

Coolant (aka Freon, but you likely have something else) is going to leak because of a bad valve or fitting, and those are likely to be disturbed during a service visit. I'll call the last repairman back out to fix it under warranty. Though if they don't have some kind of warranty on their work, you probably shouldn't have had them anywhere near their home. Fixing a low coolant issue isn't a DIY project because of the specialized equipment, licenses, and because they don't sell it to the general public.