69-1049—1
9
T8501D DELUXE ZONE THERMOSTAT
Troubleshooting Guide
(Continued).
a
Available on select models.
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 and between R and W
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.
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.
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 and between R 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 number 33. Reconfigure minimum off
time (if required).
System selection is not set to
Cool.
Set system selection to Cool.
System on indicator
(flame=heat,
snowflake=cool) is
displayed, but no
Fan operation set for 00
(conventional heat) when it
should be set for 01 (electric
heat).
Enter Installer Setup number 02 and reconfigure the fan
operation.
warm or cool air is
coming from the
registers.
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 self-test.
System on indicator
is not displayed,
but heating or
cooling system is
operating
Option not activated.
Enter Installer Setup number 36 and reconfigure to 00.
Outdoor
temperature
not displayed
a
Option not activated.
Enter Installer Setup 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.
