The kits you can buy to top up your AC gas include a gauge to check the low side pressure (gas coming from the evaporator to the AC pump). According to what I read with an ambient temperature of around 75 F the low side should be between 35 and 45 lbs and the high side between 150 and 170 on a not too hot day. Here the cheepy gauge shows a tad over 20 lbs. By this reading I should be adding refrigerant until it moved into the green area – I had already removed gas at this point. I then connected a set of regular AC gauges I picked up from Amazon for $78.
I also picked up a couple of cans of gas just in case I needed them.
The can on the left is the type that can be removed when partly used and set aside for later. The one on the right is the type that is pierced and cannot be removed. The only way to remove it is to release all the extra gas. A waste and not good for the atmosphere. The AC kit I bought has adapters for both types of cans.
The AC system was originally charged with 134A refrigerant. I couldn’t get any 134A from the parts stores, just this 12A gas which is supposed to be the replacement for 134A and can be used to top up systems already charged with with 134A
Here a low side of about 24 lbs and a high side of a bit over 175 is showing. The AC is blowing cold so I’m happy to stay with the less than optimal low side and a bit up on the high side. I may try removing some gas to get the low side down to around 20 and maybe the high side will drop closer to 170. The low and high settings are dependent on the ambient temperature. I’m using numbers for temperatures of about 75 F. The temperature when I was doing the AC work was maybe a bit higher so the high limit may be fine as is.
The system had upwards of 40 lbs on the low side when I started. That was OK per the gauge that came with the top up can kits. Once the pressure was dropped into the 20 lb range the squealing disappeared 🙂