In general, in an automotive A/C system - is there any way to determine the oil quantity?

For example:

If you buy a Fiero with an inop A/C system, find that the high pressure switch was leaking and replace it, and recharge the system - How to tell how much oil needs to be added? Any "rules of thumb"?

You don't know. If the leak was very slow and had very little oil at the site most of the time you can just recharge the system. The best thing is to take it lose at the compressor, blow the system out with nitrogen, then pull vacuum and recharge with the proper amount of refrigerant and oil. If you are replacing the compressor make sure to have it converted over to 134A.

If the compressor starts making this god-awful shrieking noise then you do not have enough. Don't ask how I know this.

quote Originally posted by Hudini: If the compressor starts making this god-awful shrieking noise then you do not have enough. Don't ask how I know this.

Your's made a warning noise?

Mine always just very quietly but suddenly slipped into the dark jaws of compressor death.

Hmm, okay. I figured it wasn't possible to tell, thought it was worth a shot though. Compressor is nice and quiet for the time being.

I assume that too much oil (within a few ounces at least) doesn't hurt anything? I understand it will reduce the cooling capacity of the system since its basically displacing refrigerant.

quote Originally posted by masospaghetti: ... Any "rules of thumb"?

"The hits just keep coming!"

quote Originally posted by masospaghetti: Hmm, okay. I figured it wasn't possible to tell, thought it was worth a shot though. Compressor is nice and quiet for the time being. I assume that too much oil (within a few ounces at least) doesn't hurt anything? I understand it will reduce the cooling capacity of the system since its basically displacing refrigerant.

Most likely ok, don't have to tell you oil can't be compressed.