A/C not working
 

My A/C stopped working a few weeks ago so when I got my brakes done the guy topped off the freon and put a dye in to find the leak.

The thing is the ac is still not working. Are there some things I can check before the garage tells me they need to change everything?

When I turn on the ac I hear a variable hum noise under the hood. Its like a droan like something is trying to engage and then not... Repeat.

Any ideas? If its a total loss I'm not dropping the cash.

the pulley clutch could be bad if its not engaging

are there any metal on metal noises? I suppose i could also be bad bearings, but i would without doubt checkout that pulley

There aren't any metal noises, just a high to low groan. The closest thing I could compare to is the sound of an engine trying to turn over with an almost dead battery.

I did read about the pulley clutch but decided to get the gases checked first.

Where is the pulley located and what do I need to do to get at it?

Have someone sit in the car and turn the A/C on while you are looking at the compressor. (Keep your hands in a safe spot)

Does the clutch engage and begin turning?

I tried this but I'm not exactly sure what I'm looking at but nothing new started turning.

See the photo, the hose the arrow is pointing at would vibrate each time I heard the noise. a vrrroooooMMMMMooooshh... vrrroooooMMMMMooooshh noise. LAMO its really hard to spell out noises!!

It's pretty obvious that it's at least trying. If it weren't, it would not be making any noise.

Is there a belt that I need to replace?

Okay.... if the A/C is not working, and the compressor is attempting to turn on but won't.... then it sounds like you may have a clutch problem.

It's so hard to actually know without being there in person.

But, if.....
The pressures have been topped off to the correct level. (not over-filled, not under-filled)
The compressor is attempting to turn on, but won't turn on...

Then there are only a few possibilities:
A) The wiring going to the compressor may be damaged (unlikely, but possible)
B) The clutch (or the compressor) is bad. It's generally easiest and best to replace the entire compressor, not just the clutch.

A shop that does QUALITY work should be able to tell you VERY quickly what the problem is. This is a fairly simple replacement, I'm not sure what book time is, but it can't be too many hours.
They will probably try to sell you a compressor, maybe some new lines, and a new accumulator/drier. A new accumulator/drier is never a bad idea.

Exactly how do they top it off if it's not working? I mean they proper way to top it off involves connecting gauges to it while it's running.

Otherwise I agree with comanche.

There's no way to properly top off the A/C system of a car without removing all the current refrigerant.... or, in other words.... the pressures of the A/C system can give you a slight indication that the system might be high or low, but there's no way to tell if its 8 oz or 16 oz low on refrigerant.... the only way, the proper way, is to remove all of the refrigerant using a machine, and then refill it to the proper level.

Also, it's measured by weight.

Sorry to thread jack, but my A.C only the last two high settings work; the rest barely blow could low refrigerant be my problem? or do i have some other problem? Sorry again about the thread jack.

Blower motor resistor, check out Cherry's FAQ's theres a link to a thread about this