A friend took his Lexus View to a local repair shop. The complaint was his wife was driving it when it started a "squeeling" noise. She turned off the air conditioner and it stopped.
When she got home he turned the AC back on, no noise, blew cold air fine.
(What do you think was the cause?)
He told the shop's manager, manager drove it around back but wouldn't let Ron go with it. A few minutes later the manager drove it back out front, He told Ron the AC had "internally exploded." The entire system had to be replaced!
He wanted $800 deposit and said the entire thing would run $1800 or more!
Ron gave him the $800, then drove it home. It would take a few days for all the parts to arrive. On the way home it worked just like normal, cold air, no squeel.
I looked at it - the idler pulley was wobbling slightly. 110,000 miles on it.
Exploded Internally? Everthing had to be replaced?
Not necessarily 'Crooks',
But they are certainly 'ASE' mechanics...
ASE guys are 'Parts Changers' by definition, they are NOT required to learn how the engine and it's sub/support systems actually work,
They are required to know some minimal diagnostic information, but very little of that.
'ASE' or 'Automotive Service Excellence' rated (ASE doesn't 'Train' Techs, they 'Test' them and give them ratings based on written tests.
No actual 'Hands On' experience necessary.
Anyway, since they are 'Parts Changers', what they do is throw parts at a problem until the 'Problem' goes away...
If there is something 'Wrong' with the 'A/C System', then you change parts in that A/C system until the 'Issue' goes away...
And since they aren't likely to be correct much of the time,
They overcharge DRAMATICALLY to compensate for the eventual, and actually inevitable, comebacks that WILL happen.
This is where an OBSERVANT 'Mechanic' that understands the systems will excell.
Now, to answer the question,
In regard to 'Idler' or 'Tensioner' pulleys,
When the A/C Compressor is turned on, it's about a 6 to 15 Horsepower draw on the engine,
All of which loads the 'Idler' & 'Tensioner' pulleys.
Idler & Tensioner pulleys have VERY SMALL, sealed bearings for the amount of load they have to deal with, and often give up...
When someone says they hear a 'Squealing' or 'Grinding' from under the hood,
The FIRST thing I check for is Flat belts or 'V' belts,
And if it's flat belts, And about all are these days,
I check the Idler & Tensioner pulley bearings.
Since a locked up power steering pump, emissions pump, water pump or alternator wouldn't have 'STOPPED' when you turned off the A/C, that rules them out immediately.
The fact that the problem was 'Intermittent' pretty much rules out the A/C Compressor...
From personal experience, I can tell you that when an A/C Compressor locks up, it's almost ALWAYS locked up FOR GOOD!
Locked compressors RARELY start turning again once they lock up the first time!
And the only other ROTATING parts that come into contact with the belts are the Tensioner and/or Idler pulleys.
(Which are about $35 when you have to replace them.)
THIS IS A VERY GOOD CASE OF HEARING 'HOOF BEATS', and thinking "ZEBRAS!",
Instead of the more obvious, 'The neighbors horses'...
$1,800 would have been high for a locked compressor, even on a Lexus...
Locked compressor means a real threat of particles in the system,
1. Replacment Compressor w/Clutch.
(only an IDIOT changes the compressor and puts a used clutch back on, ESPECIALLY if the compressor locked up!)
I get high quality, UPDATED
Remans with clutches for about $180
Or I can usually get a factory replacment for about that also...
I prefer the updated compressors with all the 'Good Stuff' inside...
Something you should change anytime the system is opened anyway.
3. Replace Orifice.
Any debris in the Orifice will make for a Comeback/Return/Warranty repair.
Since the system is open, it's no big deal anyway...
4. Flush Condenser, lines, heat exchanger.
Can't take the chance of leaving something in there that will block the new orifice or make it's way into the new compressor!
5. Flush with inert gas, Vacuum down, and Refill with coolant/lubricant.
This job may reach $800 by the time you are done, but it's by no means an $1,800 job!