No debating that proper hvac technical analysis involves the use of gauges but if you don't have access to gauges some might try the sight glass method.

In my redneck part of the world its common to equate lots of small bubbles (milky looking) as the system being low on freon. Most times the compressor clutch is not engaging due to the low pressure so you don't see anything in the sight glass. Typically we'll jumper across the low pressure switch for a couple of seconds just to make sure the system will allow the compressor clutch to engage before spending the cash for the new freon. If the clutch engages remove the jumper wire and return the 2 wires to the low pressure switch. Next add freon from the small cans watching the sight glass. When it goes from "milky" (the system has now engaged the compressor on its own...jumper wire was just a quick test) to the occasional larger bubbles we stop adding freon.

Lot's of cars in my experience have slow leaks and adding a small amount of freon once or twice a summer will keep you cool without investing a lot of time or money. This is obviously the best case scenario if your a/c isn't cooling and if you have other system problems or a large leak then it takes time, money, gauges, analysis, etc.

Another red neck solution to a common climate control failure is when some of the vaccum pods fail such that your getting heat along with your a/c (if your a/c is actually working). Those pods aren't cheap and IMHO its a pain to access them then you have to try to determine which are bad. Instead of worrying with it, sometime in May I'll clamp off the rubber heater hose headed toward the monovalve so no coolant can get into the cabin whether the system is calling for it or not. In the fall I'll remove the clamp so heat can work again.

Again these are cheap easy work arounds (not true resolutions) that may or may not help your situation.

Good luck!

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