Weird A/C Compressor Noise?

My truck sounds like it has a bird hanging out under the hood. I'm guessing my compressor is shot. Anyone know a reasonable way to fix it or do ya have to replace a bunch a stuff with the whole A/C unit

 

check the belts and the idler pulley. May be a simple fix.

 

I had a belt stretch to the point the idler tensioner was maxed out, allowed the belt to make a flopping noise, it sounded awful at low speeds when the engine was at load, fine on the freeway or at normal engine RPM.

 

Figured I would add to this thread.

Just recently started noticing a knocking/thumping noise.

I have a 98 v6 automatic tacoma.

It only makes the noise when the A/C is on and the transmission is in either R, D, 2 or L gear at a dead stop. With the A/C on and the transmission is in P or N at a dead stop, it doesnt make the noise.

With the A/C off in any gear, it wont make the noise at a dead stop.

Havent really looked into it yet.

Just curious if anyone has other suggestions other than what has been said.
If I figure it out ill update this.


Edit:
Ok I researched a bit more and looked over the truck more.
the sound is loudest underneath the engine area and towards the a/c compressor area. I used a 1/2" long socket extension to use as a stethoscope and heard the noise distinctly in the timing cover area.

As Darryle pointed out, the tensioner may be the cause of the noise under load at low rpm's.

I also found this thread, though its a different car and engine, still the same issue.
http://forums.nicoclub.com/noise-when-air-conditioner-is-on-t448864-30.html

Post #4 counting from bottom to top says this:
"Got mine solved: new tensioner assembly.
Had same noise in drive, at idle, A/C on or headlights on.
Replaced A/C compressor and alternator under warranty first.
Still had problem. Had tensioner assemblyt done and that solved it.
my Rogue has 20k miles.
Hope this helps."

It would make sense to think the A/C compressor/A/C clutch is the culprit of the sound because the timing belt Tensioner is in the same area.

Here is the Part #13540-62021 (for V6 engines only)

The dealers parts department in my area are closed, so ill go get one tomorrow if they have it and change it out to see what happens.

My Truck has 248K miles on it and the previous owner had the timing belt changed about 12k miles ago by toyota, however looking on the service history on the toyota owner website, they did not replace the tensioner.

Edit 2:
Well I replaced the Tensioner with a new one and still making the sound. Bummer... Sucks to be wrong, At lease that can be eliminated. Oh well, at least it wasnt to much work, didnt have to take anything off but the lower engine shields. I have small hands so I was able to reach in tight areas. My only other guess is it could either be the A/C compressor or the A/C compressor clutch. The Clutch when engaged does spin wobbly however the pulley spins centered.

Guess ill take it in toyota and see what the mechanic says.

 

Alright back again for another update.

Decided to tinker around more with solving my problem. Irritates me when I cant figure something out like this especially if it turned out to be a major problem. Did some more researching and figured maybe the knocking noise is coming from the torque converter or flex plate. Took the cover off and checked all the torque converter bolts. Decided that I am not taking the tranny out right now to look at the bolts for the flex plate, also the noise was strongest at the front of the engine. So I decided to check all the pulleys, thinking that the crank pulley might had gone bad or is loose. After checking all the pulleys up front, turns out the problem was the A/C pulley. Bearing must of gone bad... Glad it isnt a rod knock, would be extremely pissed if it was.

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