AC belt My AC belts break constantly. I replace with a new belt and sometimes it only lasts a day. I have had it to a good mechanic and two specially AC shops to no avail.

First thing to check is the alternator. With it securely mounted in place (and tight) grab the pulley and see if there is any play in the pulley. Excessive movement would indicate a bearing has worn out inside the alternator and that alone is enough to throw the belt off. The "better route" here is to replace the entire alternator assembly. It may should silly to replace the entire assembly for one bad bearing, but it takes less time and you get all new stuff with that replacement. There will be a core charge from the parts store, so take the old one in with you. Compare the new one to the old one to be completely certain you have the part you need and to avoid an additional trip back to get the core charge.
"Yes, you can replace the bearing itself, but why spend all day pulling the alternator, splitting it apart, pressing out the bad bearing and pressing in the new one? At the end of the day, you only to replace ONE new part in a component with several other worn (but still good) parts. Those other components will eventually fail."
If that checks out, look at your idler pulleys and your tensioner pulley. These wear out too. The difference in the two is that one is fixed and the other is spring loaded to provide the correct amount of tension against the belt. If one of these is worn / broken it would throw the belt off.
IF all of this checks out ... check for a locked up AC compressor pulley / clutch on the AC compressor. Check for excessive movement / play on the power steering pulley or the water pump pulley as well. With a high mileage vehicle, these components will be worn and may be worn out.
Lastly ... since you have to pull the belt off of the engine and need to replace something, you might as well replace the belt itself. Look into the ribbed area of the belt. If you see any cracks in the ribs of the rubber the belt strength has been diminished by more than 50% and it should be replaced.
If you live in a climate where you have all four seasons, the constant strain of heat and cold on the rubber belt also breaks down the rubber compound and over time it will fail. It is a good idea to replace it periodically. Personally, I replace my belts every two years and I keep the old belt in the vehicle just in case the new one breaks. Sometimes vehicle breakdowns happen after the parts store is closed and NEVER happen in the parts store parking lot.

You may do better to work on your own vehicles

Look for a worn crank damper pulley or & all
pulleys, that the belt your having trouble with
rides on.

No reason at all for a belt to break & not check
why, before installing a new one

What your looking for is alignment & good spring
on tensioner

Year make and model ??
The belt could be glazed and slipping even if it is tight.
You could have a weak belt tensioner too.
The noise when the ac or heat is turned on can be the extra load from the ac compressor or the alternator. The compressor cycles on and off especially in defrost mode.
The load from the alternator is the first noise of the day. As the belt warms up it becomes better at handling the load of the accessories.
Even tho the belt looks fine, you may have to replace it to get rid of the noise.

if a drive belt breaks, the debris can interfere with other engine components and do additional damage. rule of thumb belt life is 6yrs or 60000 miles. the belts operate critical engine systems ( alt, water pump, power steering pump) not something to short cut on. belts are noisey when cold due to additional load from battery use when starting or cold fuuids. have belts and tensioners checked for wear and correct operation

if the compressor bearing seized or fell apart than that would cause the belt to break or fall off. You cannot bypass the a/c compressor with a shorter belt. You can either replace the compressor or get a compressor bypass pulley but then you will not have a/c ever again until you install a compressor.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

I'd leave most of it to the mechanic.

The most likely cause is a timing belt change that was badly done in the past.

You could ask the mechanic

- to use a good quality new timing belt eg Dayco
- to change the water pump if it was not done in the last 100000 mi or so. It is behind the timing belt, so a good opportunity.
- if the timing belt tensioner should be changed too. They do weaken.
- if threadlock should be applied to the crankshaft pulley bolt. Toyota does do that at the factory.
- to check for oil leakage at the crankshaft nose oil seal. This can be changed while the pulley is off.

It is common practice to replace belts that are 3 years or older depending on the type belt it is. The stretch and break over time with heat and cooling that goes on. Some mechanics are not trained in the proper maintainance of belts and hoses You should be having the timing belt change to. I believe if it is the ribbed type belt it is supposed to be replaced at 60 thousand miles. If you don't and the belt fails it's a $3000.00 repair minimum so $200.00 IN maintiance is in my opinion worth it. And belts can just fail even new ones. However you could also have a Tensioner pulley bearing going out causing the problem so I suggest you try a different shop. Hope this helps and thanks for using fix-ya.

The squeeking is most likely coming from your belt's idler pully. They cost around 10 bucks and are attached with one bolt. Kinda hard to get to, so be patient.

clutch

the ac belt is sperate from the power steering belt.. sounds to me you need to replace the belts (both of them) but theres a idler pully in the middle of them all witch may have a bearing going out on it..i had to change mine at about 85,000.. when i had the belts off i spun the pully and it was excessivly stiff cause'n slipage and also a squel.. hope its not the alt, or water pump making the noise..they can run ya into some $$