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Ambient Sensor
The ambient sensor (T5) provides the control with a
reading of room temperature as the evaporator fan
draws air through the machine housing.
The control checks the sensor to conrm:
1. Ambient temperature is between 45°F and
120°F.
2. The T3a, T3b and T5 sensors are all within 15°F
of each other before the compressor starts.
3. The condition of the sensor is either open or
shorted. The sensor is considered open if the
voltage at control board location T5 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.
Specic failures associated with the ambient sensor
can initiate fault code Fd and F8. (See Service Mode.)
The sensor is attached to the bottom of the junction
box with a plastic wire tie.
The front shroud must be removed to access the
ambient sensor. (See
Machine Compartment Covers.)
Ambient Sensor
Upper Element Cover
(Continued Next Page)
Junction Box
Wire Tie
Thermal Cutout (TCO)
The TCO provides additional safety from the tank
overheating.
The TCO is located between the T2 tank sensor and
the upper element. (See Component Locator Views.)
The TCO opens at 170°F and operates as a double
line break that opens L1 and L2 voltage.
If the TCO opened, it will disable the entire unit,
including power to the control. The TCO requires a
manual reset.
If the TCO has opened, suspect a shorted relay on
the control board, or problems with the T2 tank
sensor, compressor, upper and lower elements,
or failure of the TCO itself. Do not just reset the
TCO without determining the reason for the circuit
opening.
To replace TCO:
1. Remove the two T-20H Torx security screws and
the upper element cover.
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