Want at recharge my air conditioning

It is never good to mix the two different freons. Therefore, you will need to vacuum down the system in case there is any R12 left in it. Next, there is a retrofit kit that will be needed. Basically, it adapts to the low and high side ports so the new type fitting can be used on your system. Once that is done and all R12 has been vacuumed from the system, you can add the 134A with no problem. I will say that it won't cool as well as the original Freon, but it gets the job done. Keep in mind, there could be a leak or other problems with the unit. Keep it under a vacuum and see if it holds for at least 20 minutes. If it doesn't, there is a leak. If it does hold vacuum, recharge it and see if it works. Using gauges, you want the low side pressure to be around 40psi and the high around 150psi. These pressures will change on weather temps and humidity, but you should be close.

Let me know if you have other questions.

Joe