69-1052—1 8

T8511G DELUXE HEAT PUMP ZONE THERMOSTAT

5. Press the increase ▲ key again to display the
EEPROM identification code.
6. Press and hold the increase ▲ and decrease ▼
keys together, until the room temperature is
displayed, to exit the system-test. The system-test
times out after ten minutes without any key presses.

TROUBLESHOOTING GUIDE

CHECKOUT

Outdoor Temperature Sensor

(Where Applicable)

Allow the outdoor temperature sensor to soak in the
outdoor air for a minimum of five minutes before taking a
reading. With an accurate thermometer (±1°F [±0.5°C]),
measure the temperature at the sensor location, allowing
time for the thermometer to stabilize before reading. Match
the thermometer reading to the outdoor temperature
display at the thermostat.
(Continued)
M4867
aAvailable on select models.
Symptom Possible Cause Action
Display will not
come on. Thermostat is not being
powered. •Check that C terminal is connected to the system
transformer.
•Check for 24 Vac between C and R terminals.
—If missing 24 Vac:
—check if the circuit breaker is tripped—reset the
circuit breaker.
—check if the system fuse is blown—replace the
fuse.
—check if the power switch on the HVAC equipment
is in the Off position—set to the On position.
—check wiring between thermostat and HVAC
equipment—replace any broken wires and tighten
any loose connections.
—If 24 Vac is present, proceed with troubleshooting.
Thermostat microprocessor is
locked up. Remove the thermostat from the wallplate for 2 minutes. After
2 minutes, replace the thermostat on the wallplate.
Temperature
display is incorrect. Room temperature display has
been reconfigured. Enter Installer Setup number 37 and reconfigure the display.
Thermostat is configured for °F
or °C display
a
.Enter Installer Setup number 14 and reconfigure the display.
Bad thermostat location. Relocate the thermostat.
Temperature
settings will not
change. (Example:
Cannot set the
The upper or lower temperature
limits were reached. Check the temperature setpoints:
•Heating limits are 40 to 90°F (4.5 to 32°C)
•Cooling limits are 48 to 99°F (7 to 35°C).
heating higher or
the cooling lower.) The setpoint temperature range
stops were configured. Check Installer Setup numbers 34 and 35 and reconfigure the
setpoint stops.