GE GEH50DEED Technical Service Manual page 45

Tank Sensor
The tank sensor (T2) is located above the thermal
cutout (TCO) and provides the control with a
resistance value for determining tank temperature.
it is the only feedback the control has for tank
temperature.
Just before the compressor starts, the control
checks to ensure T2 sensor temperature is between
30°F and 160°F.
The sensor is considered open if the voltage at
control board location T2 is greater than 4.88 VDC
and shorted if less than .098 VDC.
A T2 sensor fault is considered a critical failure and
will completely shut the system down, causing no
hot water.
Specific failure associated with the tank sensor can
initiate fault code F2. (See
The sensor is held to the tank utilizing a bracket that
is attached with a 7/16-in. hex nut on the left side
and a 3/8-in. hex nut on the right side. Two 1/4-in.
electrical terminals are connected to the sensor.
T2 Tank Sensor
Bracket
TCO
Note: During production, thermal paste is used
under the tank sensor to provide additional
conductivity between the tank and the sensor.
it is not necessary to apply additional paste if the
sensor needs to be replaced.
Thermal Paste
Service Mode.)
Evaporator Inlet Sensor
The evaporator inlet sensor (T3a), provides the
control with evaporator inlet temperature during
sealed system operation.
The control checks the sensor to confirm:
1. Evaporator is frost free (above 32°F) at
compressor startup.
2. Evaporator inlet is greater than 20°F after 30
minutes run time.
3. Temperature difference between T3a and T3b is
greater than 5°F after 30 minutes of run time
4. Using T5 ambient sensor, verifies T3a is at least
10°F less than room temperature while sealed
system is running.
5. The T3a, T3b and T5 sensors are all within 15°F
of each other before the compressor starts.
6. The EEV is operating properly and valve rotation
is within range.
7. if the sensor is open or shorted. The sensor is
considered open if the voltage at control board
location T3a is greater than 4.88 VDC and
shorted if less than 0.098 VDC.
if any of the above tests fail, the control will stop
the sealed system and operate the water heater in
electric mode.
Specific failures associated with the evaporator inlet
sensor can initiate fault codes FC, Fd, FF, and F5.
(See
Service Mode.)
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