T8501 MICROELECTRONIC THERMOSTATS
11 69-0925—4
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 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 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
is displayed, 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
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.
Outdoor tempera-
ture not displayeda
Option not activated. Enter Installer Setup numb er 24 and set to 01. Thermostat must
have OT terminals and a C7089B1000 installed.
Outdoor
temperature
display is incorrecta
Outdoor sensor is connected
incorrectly.
Refer to C7089B1000 installation instructions and check wiring
between the thermostat and sensor.
Wrong sensor. Replace sensor with C7089B1000 sensor.
aSelect Models
Table 5. Troubleshooting Guide. (Continued)
Symptom Possible Cause Action