Troubleshooting Guide; Outdoor Temperature Sensor - Honeywell T8511G Installation Instructions Manual

5. Press the increase
EEPROM identification code (Example: 222 =
EEPROM ID 222).
6. Press and hold the increase
keys until the room temperature is displayed to exit
the system-test. The system-test times out after five
minutes without any key presses.

TROUBLESHOOTING GUIDE

Symptom
Display will not Thermostat is not being
come on. powered.
Thermostat microprocessor is
locked up.
Temperature Room temperature display has
display is incorrect. been reconfigured.
Thermostat is configured for °F
or °C display
Bad thermostat location.
Temperature The upper or lower temperature
settings will not limits were reached.
change. (Example:
Cannot set the
heating higher or
The setpoint temperature range
the cooling lower.)
stops were configured.
Heating will not No power to the thermostat.
come on.
a
Available on select models.
key again to display the
M4867
and decrease
Possible Cause
a
.
MICROELECTRONIC HEAT PUMP THERMOSTAT
CHECKOUT

Outdoor Temperature Sensor

(Where Applicable)
Allow the outdoor temperature sensor to absorb 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.
• Check that C terminal is connected to the system
transformer.
• Check for 24 Vac between C and R or RH 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.
Remove the thermostat from the wallplate for 2 minutes. After
2 minutes, replace the thermostat on the wallplate.
Enter Installer Setup mode number 37 and reconfigure the
display.
Enter Installer Setup mode number 14 and reconfigure the
display.
Relocate the thermostat.
Check the temperature setpoints:
• Heating limits are 40 to 90°F (4.5 to 32°C).
• Cooling limits are 48 to 99°F (9 to 37°C).
Check Installer Setup mode numbers 34 and 35 and
reconfigure the setpoint stops.
• Check that C terminal is connected to the system
transformer.
• Check for 24 Vac between C and R or RH 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 system switch at the equipment is in the
Off position—set to 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.
9
Action
(continued)
69-0961—4