Filter
Top Products
69-1055-1
9
T8524C,D MULTISTAGE MICROELECTRONIC THERMOSTATS
Symptom Possible Cause Action
Heating will not
come on.
No power to 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 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.
Heating will not
come on.
Thermostat minimum off time is
activated.
Wait up to five minutes for the system to respond.
System selection is not set to
Heat.
Set system selection to Heat.
Heating setpoint is below room
temperature.
Check heating setpoint. Set heating setpoint to desired
temperature.
Cooling will not
come on.
No power to the thermostat. • Check that C terminal is connected to the system
transformer.
• Check for 24 Vac between C and R or RC and Y 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 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 minimum off time is
activated.
•Wait up to five minutes for the system to respond.
• Enter Installer Setup mode number 33. Reconfigure
minimum off time (if required).
System selection is not set to
Cool.
Set system selection to Cool.
Cooling setpoint is above room
temperature.
Check cooling setpoint. Set cooling setpoint to desired
temperature.
Heating or cooling
comes on
momentarily and
shuts off
Heat or cool circuit is opening
up or becoming high
impedance.
Add resistor in parallel with load or install interface relay.
System On
indicator is lit, but
no heat is being
delivered.
Fan operation set for 00
(conventional heat) when it
should be set for 01 (electric
heat).
Enter Installer Setup mode number 02 and reconfigure the fan
operation.
Conventional heating
equipment turns on the fan
when the furnace has
warmed up to a setpoint.
Wait a minute after seeing the On indicator and then check the
registers.
Heating equipment is not
operating.
Verify operation of heating equipment in system test.
Outdoor
temperature
not displayed
a
Option not activated. Enter Installer Setup mode number 24 and set to 01.
Thermostat must have OT terminals and a C7089B1000
installed.
Outdoor
temperature
Outdoor sensor is connected
incorrectly.
Refer to C7089B1000 installation instructions and check wiring
between the thermostat and sensor.
display is incorrect
a
Wrong sensor. Replace sensor with C7089B1000 sensor.
TROUBLESHOOTING GUIDE (Continued)
a
Available on select models.