Questions about sound from under hood when A/C is ON

I have a 2001 Toyota Tacoma V6 4x4 with about 290,000 miles on it

Last week while on a road trip in southern Virginia I heard an odd sound coming from under the hood. Seems to go away when I turn off the AC.

Here's a video I took recorded from under the hood when I discovered the sound:



^ In the beginning of the video you are hearing sounds under the hood with the AC OFF then I go inside and turn AC ON and you hear what made me think the compressor needed lube.

I immediately stopped by Walmart and added about half a 3 OZ can of R-134a Refrigerant and "Oil charge" consisting of PAG Oil (Polyalkylene Glycol) to the AC low pressure charge valve with the blower on high and AC ON as instructed on the can.



Its now been several days and there seems to be an improvement as I don't hear that exact sound anymore but sometimes the sounds can still be a bit off coming from that area.

It's been very warm this week but I have been trying not to run the A/C to much till I could post this question...

Is something failing???

Air conditioner has been working great all this time and never failed at any point before this point or now. The fill level which is shown on my refill adapter states "filled" which is in the correct range as per the standard fill tool/gauge pictured and the AC blows cold and seems to functions normally.

Other than refilling the refrigerant every other season or so I've never serviced the AC in the tens years I've owned the truck.



^ This is what it sounds like today... The beginning of the video is with the AC ON after which I turn it OFF...

It currently doesn't sound as bad as before since I added the R-134a Refrigerant and oil charge. But could it be a temporary fix and so got me worried about my AC and what causes this sound and if there is anything else I should check or know.

Any help is appreciated

Yormosi

 

I would start with the ac idler pulley, typically these go out 1st and it’s an easy fix and the sound will change as the pulley heats up or is cold

 

Check your AC belt. Embarrassing to share but my AC sounded like a cricket chirping in a tin can whenever the compressor clutch was engaged. Turn the air off and it sounded fine. I really couldn’t locate the source of the noise with a stethoscope so I fired the parts cannon and replaced the idler pulley. No improvement. Replaced the clutch on the compressor and no improvement. At that point I was sure the compressor was going to grenade and really cause havoc so I replaced the compressor and drier. No improvement. I thought the only thing left is the harmonic balancer but luckily I took a notion to replace the all my belts and wouldn’t you know it, problem solved. There was no noticeable wear or cracks in the old belt but it was the source of my problem.

 

had a screeching sound when a/c was engaged. thought it was compressor or clutch or pulley or belt. turned out to be bad harmonic balancer at 210Kmiles. 2004 tacoma prerunner

 

You have a leak in time it will get to the point of no longer holding a Charge.

Just know that day is coming .

Checking the idler bearing the Clutch and belt is always a good idea.

 

How can you be sure of that?? AC has been holding a charge for YEARS. Of course some refrigerant might escape but NO SYSTEM is 100%. Physics does state if you wait long enough anything that could happen indeed will.

Confused about this... Are you stating: "Checking the idler, the bearing, and the clutch and belt is always a good idea." ?????


thanks