Prove Out Your Troubleshooting Diagnosis
Troubleshooting refrigeration systems can be problematic at times. Misdiagnosing a system can be expensive to both you and your customer. As a service technician, it is important to verify that your diagnosis is correct. This is not always possible or easy to achieve, but it should be done. There are two basic ways in which you can verify your diagnosis: when possible, the suspect component can be temporarily jumped out, or an additional test can be done to verify your analysis.
Defective controls are the easiest to verify. Simply jumping out the suspect control will verify if it is the problem. Be careful, not all control components can be left jumped out. This is especially true of any safety control—it may be jumped out for a very short period just to verify your diagnosis but not left that way. You must use good judgment when jumping out any component.
Mechanical components are more difficult to verify since they cannot be simply jumped out; however, a technician can verify a diagnosis by performing an additional test. For example, if a single-phase compressor fails to start and the technician has measured the correct voltage and resistances at the compressor, he may determine that the compressor has internally locked up. This may well be true. However the starting relay or start capacitor (where used) may also cause the compressor not to start. The technician should attempt to start the compressor with his own starting kit. If the compressor still fails to start then they can be comfortable that it is defective.
Repairing refrigerant leaks and verifying that the system is leak free is important but not always easy. Sometimes there is more than one refrigerant leak in a system. If a technician finds one leak, repairs it and charges the system, he could be back on the job again shortly looking for another leak. This is costly for the technician and the customer. There are two methods to aid a technician in verifying that a system is leak-free. One is a standing pressure test: after all the refrigerant has been removed, dry nitrogen is introduced into the system and observed over a period of time. If the pressure remains the same the system can be assumed to be leak-free. Another test is to pull a deep vacuum on the system: using an electronic micron gauge, pull a vacuum on the system down to approximately 500 microns. Once this level is achieved leave the system idle and observe your micron gauge. If the gauge reading begins to rise and steadily continues to rise, there is another leak in the system. If the micron gauge rises for a brief time and then levels off, you may have repaired the leak but the system may still contain moisture and will need to be dehydrated further. Simply continue to pull a vacuum on the system and repeat the test.
Verifying your diagnosis will take additional time, but this is time well spent. It will actually save time and money for both you and your customer. It will reduce the amount of callbacks and reduce the replacement of non-defective components on the job. It will also allow you to leave the job with peace of mind knowing you have made a correct diagnosis.
