Low port to recharge air conditioning system

The correct port will be the one that has the smaller of the two outside collars on the charge port. Also if you have one of those diy charge hoses it will only fit on the low side which is where you charge it.

Was the system empty when you started charging it?

You always take a pressure reading before doing any charging etc. You have to check the high and low pressures both the tv comercials and auto parts stores have thinking buy this can of charge and it will solve all your problems. But you have variables is the system actually low on charge?Or is it a pressure issue wiring issue high low pressure switch issue. Does it have a leak?If I put a can in is it now over charged and still wont work properly?The only way to tell how much is in the system is to have it recovered by a ac machine and the charge is weighed by the machine.A pressure reading doesnt tell you when its full I know it says it on the diyer charge hose gauges but its not dead on.