I'm not mechanically savvy. I'll admit it, right away; likewise, I don't like to mess with anything mechanical, for fear that I would just ruin it.
Having said that, I feel like there is something wrong when an A/C unit, that did not make a loud screeching noise suddenly starts making one, out of the blue, for no real reason.

I don't intend to start trying to repair the thing (like I said, I'd probably kill it, dead), but I would like to try and find out what the problem could be. Reason being, this was a recently (as in, 4 days ago) repaired unit; I want to know if this is something that could have developed on its own or not.
Because I'm paranoid like that.

Information that could help?

• It is a Lennox model unit.
• It makes the noise when the air conditioner is on, but it isn't constant. The noise pulses from anywhere between 3-10 seconds, then stops periodically for anywhere between 2-4 seconds.
• This noise does not happen if it is set to fan-only.
• This noise only happens with the outdoor unit.
• If the air-conditioning unit is cooling, it does blow cooled air.

Any other information, I wouldn't know to give, or wouldn't know on hand; if I need to give more information, please let me know and I'll try to get some more. At the moment, the unit is off in an effort to preserve anything that can be salvaged.

 

What was just repaired? It sounds like it could be dry bearings in the outside fan, but it would take a closer listen to be sure.
When your thermostat is set on fan only, the outside unit is off and only the furnace blower is running.You might want to call the repair shop, but first figure out what they repaired and charged you for. It could be coincidental - or not.

 

They left the sheet metal screws loose in the condenser fan and the blade is rubbing so get them back out there to replace all damaged parts