Squealing air con belt

Hi all, I have one of those annoying problems that mechanics are having trouble working out.

When Air con is on and underload it squeals. Following steps have been taken so far;

1. Belt replaced and tightened, last 1 day,
2. 2nd belt and tightened, last 1 day,
3. Tension pully replaced, lasted 5 days
4. Today Air con guy checked over A/C compressor and affliated A/C parts and could not find any issues. He retensioned the belt so far has lasted 30min and still ok.

I have contacted a Toyota service advisor and have be told the Tensioner pully bolts might need to be replaced to to worn threads or bent. I plan to check this if and when it starts squealing again (don't touch whats not broke)

So anyone out there heard of this issue.

Being in Darwin the A/C is quite important and so is my marriage lol.

Cheers
Paul

Maybe the pulley has worn and allows the belt to touch the bottom once it has run for a while?

If it recurs try the bolts or a slightly wider belt.

I had a similar problem when we fist got it, but a quick tighten and so far all is well.
Clive has a good point tho, if the belt is bottoming in pulley you can't tighten it properly.

Mine does the same so I will try the suggestions too.

(not quite as important in Bristol at the moment)

We live on a good sized hill, so I use the aircon as a engine brake going down. Turn both front and back on and it saves on brake linings... You can take the boy out of the truck but you can't take the truck out of the boy

Well it's been 3 days touch wood. Thanks for the advice, if it does start again i'll try the above.