1993 Ford Aerostar Air conditioning

First of all thank you so much for your donation. Here's the problem you can't tell how much charge is in the system by what pressure you have. Pressure is only used for diagnostics purposes to trouble shoot problem's or to see that the system pressure is good and within spec's. The only way to tell if the system has the correct amount of charge is to get a a/c recover machine which cost's a couple of thousand and recover the charge. Then you would pull a nice long vacuum on the system to help remove water from the system. Then you watch the gauge's for 5 min's to see if you had a leak by seeing if the system was loosing vacuum. Then the machine would charge the system by weight it has a built in scale. Unless your system is totally empty you used the right amount of can's then you would know it was full to the proper level.

What i'm trying to say is to do right yes you do. The point I was trying to make was the pressure gauge can't tell you when the system is full of charge. You could have too little or too much and you wouldn't be able to tell with the pressure gauge. The low side where you would fill it it's normal pressure with the compressor running is 20-50 psi. Also when you read the pressure you have make sure the valve is turned off to the can so your not reading the can's pressure. Unless the can is empty. With some of those charging hose's the gauge is the valve. On your car it take's R-12 Unless it was converted to R-134?They no longer sell R-12 in the store they only sell the r-134. If your hose's have threaded nipple's on them for charging or checking the pressure then you still have it set up for r-12.

NO if you hook it to the high side the can could explode you always hook it to the low side to charge it. If you have never charged a/c before you might want to get someone that has done it before help you.