Capilliary Tube (Cap Tube) Issues
All compression refrigeration systems depend on some device to separate the high and low pressure sides of the system. In a capillary (cap) tube system, this is the capilliary tube itself, which, as the name implies, has an extremely small micro-bore at its center that is less than the diameter of a needle.
There are two main issues that can occur with cap tubes: a particle blockage at the high pressure end near the compressor (picture on the left), and a moisture, wax, or oil problem at the other next to the evaporator (picture on the right). The Guide below describes the symptoms and recommended remedies for cap tube problems.