One very common upright freezer problem is a frozen evaporator coil.
If you're on a troubleshooting call for an upright freezer with this problem:
While the coil is still cold, set the defrost time to 2 minutes, put the unit into defrost, take an amp draw on the heater element to make sure it's working, and then wait for the timer to time out and terminate the defrost cycle.
If the defrost timer doesn't terminate the defrost cycle, the timer has failed and must be replaced.
If the timer terminates the cycle, set it to a point where it's within a minute or two of initiating a defrost cycle, then wait and verify that it will cycle into defrost.
If it does, you've verified that the defrost timer will cycle into defrost, the heater element works, and the timer will cycle out of defrost.
After the ice is melted off, check the evaporator fan and make sure it runs, and that the blade is the right size, and turning in the right direction.
Make sure air flow through the unit and the evaporator coil isn't blocked.
If your upright freezer has a heater in or on the evaporator drain tube, verify that it is wired correctly, and that it works.
It should be wired to be on all the time.
Verify that there is a trap in the drain tube.
This prevents outside air from migrating to the evaporator coil.
Finally, make sure the gaskets all seal correctly, and that outside air isn't migrating into the freezer.
By the time you've completed all of these checks, you should have found and corrected the problem that was causing the evaporator freeze-ups.
If your upright freezer seems to have lost cooling capacity, make sure the evaporator and condenser coils are clean and that air flow through the coils is not blocked, make sure that the evaporator and condenser fan motors are running at the correct speed, and that the fan blades are the right size and turning in the right direction.
If there are supposed to be shrouds on the fans, make sure they're installed correctly.
If there is no shroud to guide air through the condensing coil to the fan, the unit will definitely lose capacity; and if a unit runs for very long in this condition, it will shorten the service life of the compressor.
When you're ready to check the pressures and temperatures, you might want to open and read our
System Evaluation Manual.
It has a cycle diagram and guidelines for evaluating pressures and temperatures on air conditioning and refrigeration systems.
You might also want to take a look at our
Refrigeration and Electrical Troubleshooting Chart,
which is re-printed from a military training manual.
I hope this page has helped, and please, feel free to contact us with any specific HVAC questions you might have, including questions about refrigeration on Guam, and air conditioning on Guam.
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