If troubleshooting requires measuring the system’s refrigerant pressure, first identify the type of refrigerant being used. This could lead to the first major challenge. If the refrigerant type is not known, it will not be possible to accurately determine whether the pressures, superheat, or subcooling values are correct for the system.

Another potential obstacle can be attaching refrigerant gauges to the system. Some of these systems may have had access ports left uncapped for years, making their threads unusable. If reading the pressure is a must and there is no other access port to use, add a saddle valve to read the pressure; however, it is not a good practice to leave these valves on permanently. A plan should be developed to remove these valves at some point and install a permanent access or replace the service valve.

The stems of some older service valves can also be problematic. These older service valves can leak refrigerant around their stems when placed in a mid-seated or front-seated position and occasionally when placed back in their backed-seated position. Some service valves do have packing nuts that can be tightened, but some do not, so this can become a real issue. If the valve was not leaking refrigerant before you touched it and now it leaks, this problem can sometimes be solved with the stem cap and some good pipe dope, but not always. Because of this potential, always check the service valves before leaving the job and make sure they are not leaking.

Occasionally you may come across a system with incorrect components installed. One time I was working on an older reach-in cooler installed at a local bar. The system had a refrigerant leak, which is a pretty typical issue for this type of equipment. As I was looking for the source of the leak, I noticed the system had a TXV metering device — not too unusual — but connected to the outlet of the TXV was a capillary tube metering device.

Apparently this system had been working this way for a while, so I was faced with an issue: Do I simply repair the leak and recharge the system, leaving the two metering devices installed, or do I remove one of the metering devices, repair the leak, and recharge the system? Of course, the only real choice was to remove the second metering device. But this did require additional time and, more importantly, a detailed explanation to the bar owner why this was necessary, since it had been working for some time with the two metering devices installed.

Servicing older systems can definitely be challenging at times. Think twice as you go through the system, and be on guard for potential issues that could arise. As you come across these problem areas, have a backup plan ready for when things go sideways. Otherwise, simple problems can become major issues for you and your customer.