Automatic Temperature Control (Atc) - GE GTUP270EMWW Technical Service Manual

Automatic Temperature Control (ATC)

• The automatic temperature control (ATC) is a feature
that utilizes a thermistor to regulate the water fi ll
temperature.
• The thermistor has a negative temperature
coeffi cient (as temperature increases, resistance
decreases).
• The thermistor is located in the outlet of the fi ll
funnel and will measure 50K
(77°F / 25°C).
• If the thermistor reads outside the expected range
(10K - 120K ), the main control will default to the
following pre-programmed fi ll temperature settings:
Tap Cold = cold water valve only
Cold = cold water valve only
Cool = hot and cold water valves
Warm = hot and cold water valves
Hot = hot water valve only
• When both valves are energized, the internal orifi ces
in the valves meter the fl ow to a 60% cold and 40%
hot ratio.
• With the lid open, ATC is deactivated.
• Extreme water temperatures at low pressure can
cause the ATC to use its maximum number of
activations and revert to a preset fi ll routine. The
main control will not allow the water valve to cycle
more than 25 times per fi ll.
Resistance can be measured at the wire harness
located on the control board location J12. Make sure to
unplug the connector to isolate the thermistor before
taking resistance readings.
To determine the temperature of the incoming
water, the main control measures the difference
between the voltage sent and the voltage returned
from the thermistor. The main control then makes
temperature adjustments accordingly.
The main control should fi ll the tub with water within
+/- 10 to 15°F of set temperature by opening or
closing the hot and cold water valves.
at room temperature
To remove the ATC thermistor:
Note: To replace the ATC thermistor; the entire unit
must be removed from its location.
1. Remove the entire unit from its location.
2. Remove the control panel. (See
3. Remove the Phillips-head screw located to the
Note: The water inlet funnel is attached inside the
unit with 2 Phillips-head screws. The ATC sensor
wiring utilizes 3 wire ties.
– 54 –
ATC Temperature Chart ATC Temperature Chart
Temperature Setting
Tap Cold
Cold
Cool
Warm
Hot
right of the harness entry.
Harness Entry
Wire Ties
Water Temperature
Cold Tap Water
60°F ( +/- 10°F )
70°F ( +/- 10°F )
80°F ( +/- 10°F )
110°F ( +/- 15°F )
.)
Control Panel
(Continued Next Page)