Abnormality of superheat due to low discharge temperature

What does U7 mean?

This fault occurs when the discharge superheat remains at or below -15˚C (5˚F) continuously for 3 minutes, even after the linear expansion valve has reached its minimum open pulse and the compressor has been operating for 10 minutes. This indicates insufficient superheat, potentially due to issues with the discharge thermistor, linear expansion valve, or refrigerant charge, which can lead to liquid refrigerant returning to the compressor, risking compressor damage.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Verify the operation of the linear expansion valve itself. If it appears defective, it may require replacement. Refer to section 10-6.