It’s mostly fine, air is working and nice and cool.
Intermittently, it’s making a high-pitch squealing noise. Goes away, comes back. Not always at start up, either. It just kind of happens. I’m literally so ignorant, I was tempted to go WD-40 that sucker.
Sounds like the cooling fan bearing. You probably won’t get wd40 into it in sufficient quantities to do any good without disassembling. Besides that, WD40 is not the best choice for spray lubes anyway. Depends on how mechanically inclined you are as to the next step. I’d try to change the bearing but it might be easier for you to swap out the fan. Unplug the fan if possible to see if the noise returns. Your heat exchanger would be almost useless there so if you do it for a long time, I’d mist a little water on it now and then.
I’d have no idea as I do almost all my own repairs. A technician would be able to diagnose it and get repair parts a lot faster most likely. It would help if you had diagnosed some of it before you call and if you had the part number from the owners manual so he could have one on the truck.
I replaced the fan motor on my unit, which incidentally looked something like yours, a few years ago myself. The fan motor died, apparently because of bad electrical connection (the wires were badly oxidized), so I took a picture of the motor plate with a digital camera (this was before they were included on everyone’s phone) and went to the closest electrical supply shop and showed them the picture. I got a new fan motor for something like $80 and installing it was easy with simple hand tools (just make sure you pull the breaker AND turn off the thermostat).
Using my simple calculation of prices are likely 20% higher than they were, your technician is likely to markup the motor about 50%, and labor cost equals part cost, I’d estimate it will cost you $300. Of course, labor rates will vary widely, depending on your location. I guess the take away is if you are comfortable doing it yourself, it’s pretty easy. If you aren’t, you had better call a technician.
Finally, you do know that it is going to wait until a Saturday afternoon on one of the hottest days to give up the ghost, don’t you? It’s probably worth a $80 service call to have a technician take a look at it while it is still working to allow them to schedule the repair when they aren’t super busy.
ETA: The usual life of a central air unit is about 20 years. You are due for a replacement. Usually, that means inside and outside unit replacements. If you own this property and plan on staying there for a while, you might consider looking into replacement. Yeah, $300 is a lot cheaper and it may be the best option, now. But, a new unit may be in your future.