GE GEH Series Service Manual page 40

The T4 compressor outlet sensor provides the control with
compressor discharge temp during sealed system operation.
The control checks the sensor to confirm:
1. Outlet temp has risen at least 20°F during the 1 30 min
st
2. Outlet temp is greater than 120°F after the 1 30 min
st
3. Outlet temp never exceeds 240°F while operating
The sensor is considered open if the voltage at the board is
greater than 4.88VDC and shorted if less than .098VDC.
If any of the above tests fail, the control will stop the sealed
system and operate the water heater in electric mode.
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