Honeywell CHRONOTHERM IV DELUXE T8624D - Manual (Page 18)

T8624D CHRONOTHERM ® IV DELUXE PROGRAMMABLE THERMOSTAT
68-0166—1 18
TROUBLESHOOTING GUIDE
Refer to Table 12 for troubleshooting information.
Table 12. Troubleshooting Information.
Symptom Possible Cause Action
Display will not
come on. Thermostat is not being powered. • Check for 24 Vac between R and C 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.
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. Enter Installer Setup number 14 and reconfigure the display.
Bad thermostat location. Relocate the thermostat.
Temperature settings
will not change.
(Example: Cannot set
the heating higher The upper or lower temperature
limits were reached. Check the temperature setpoints:
•
Heating limits are 40 to 90°F (7 to 31°C)
• Cooling limits are 48 to 99°F (9 to 37°C) .
or the cooling lower.) The setpoint temperature range
stops were configured. Check Installer Setup numbers 34 and 35 and reconfigure the
setpoint stops.
Heating or cooling
come on momentarily
and shut 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
(flame=heat,
snowflake=cool) is
displayed, but no
warm or cool air is
coming from the
registers. Heating or cooling equipment is
not operating. Verify operation of heating or cooling equipment in system test.
Heating will not
come on. No power to the thermostat. • Check for 24 Vac between R and C 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.
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.
(continued)