AC Ticking Time Bomb

I've had this noise for a few years now. It's a sort of an irregular loud ticking from the front of the engine. It's not louder on any particular side, that I can tell. It's loudest during idle, and does speed up and quiet down with higher revs. I just discovered today it only occurs while the AC compressor is on, so it must be ready to go.

https://youtube.com/shorts/RoYq2ZuwGEM (0:43 above engine)

https://youtube.com/shorts/z3vIA6KBzNU (0:16 below engine)

Sounds like a bearing noise to me, though it could be something like a failing harmonic balancer. First video shows no visible wobble in the crank pulley, though. Any wild guesses?

 

Man, if bearing would be more consistent hum/squeal

that is more of a intermediate ticking

my internet guess is T belt tensioner

can u narrow down more exact area of the tick?
Like with
-long screw driver with your ear to the handle
Or
-mechanic stethoscope

 

I did put in a new timing belt, tensioner and idler pulleys about 5 years ago, possible I screwed something up then. But then I wonder why it only ticks while the AC is on. If I switch it off, the sound immediately stops. I switch the AC on and it comes back 1-2 seconds after. I might try adjusting belt tension and see if that helps.

 

Hmmmm

AC clutch possibly
Can u do that screwdriver/stethoscope method to confirm that tick coming from AC compressor/clutch pulley?

 

Ah, I will try that when I get back into town. Thanks for the idea!

 

I wouldn't be surprised if the compressor was making noise, it's over 25 years old