1. Relevant pressure gauges of high and low pressure, while it is stoppered, high and low pressure with R22 is same data, and pressure is about 8kg; while chiller is running, low pressure data is about 4kg, and high pressure is about 18kg; if data is much lower than this data, it means gas loop leaking, the water chiller
should be stopped immediately, and the water inside system should be fully let out; then contact with Supplier for how to checkout the leaking point and do not start the chiller again before the leaking point fixed. Avoid to lead other parts broken, especially the compressor;
2. If the pressure data is right data, then check the wiring of the pressure switch, it might be the connection loosing leads problem.
3. Pressure switch has problem, then change a new one.