1992 Sabb conv 2.1

Normally a freon top off is done by running the ac system and watching the "window". At idle the window should show steady stream of refrigerant but not fill up the window cavity. At 2500 rpm the window should be full with a fair amount of bubbles in the refrigerant. Do not charge until the window is clear of bubbles, trust me, there's a reason I know. For a properly charged and operating ac system the temperature drop from outside ambient to "cold" air side is 18 to 22 deg f. This is for a system not on recirc. Resist the temptation to just charge the hell out of it. It is better to be undercharged than overcharged. An overcharge of refrigerant will cause damage to the compressor and other components. Remember to purge the fill lines prior to hooking up the fill rig and gauges. If you are starting from scratch with an evacuated system, hook up the fill rig and start the ac system. Top off the refrigerant as if it was low. As for the amount of refrigerant in the system, I would imagine it to be less than 36 ounces. Sorry I don't have the exact figure off the top of my head. I'll see if the figure is in the book.

dave