9
TROUBLESHOOTING
Table 4 — Thermostat Troubleshooting
PROBLEM SOLUTION
Display on thermostat not illuminated. Check for 24 vac at the R terminal connection. Terminal R must be
connected for proper thermostat operation.
‘‘Service Filter’’ is displayed on thermostat. After the configured number of blower operating hours, the Service Filter
message will be displayed. This reminds the owner to replace the filter.
Reset the Service Filter feature to reset the blower operation timer to 0
hours.
Cooling will not energize. Select COOL mode. Decrease cooling set point to 10 degrees below room
temperature. Check for 24 vac at Y1 terminal with a load connected. If
present, thermostat is operating correctly and problem is with wiring or
equipment. If 24 vac is not present, replace the thermostat. Check for Com-
pressor Cycle per Hour Limit. Cooling may be locked out.
Heating will not energize. Select HEAT mode. Increase heating set point to 10 degrees above room
temperature. Check for 24 vac at W1/O/B terminal with a load connected. If
present, thermostat is operating correctly and problem is with wiring or
equipment. If 24 vac is not present, replace the thermostat.
When using 4 wires (R,G,W,Y), the cooling equipment
tries repeatedly to turn on, but cannot. At times the
display dims or disappears.
There is not enough power available. Connect a 270 ohm, 10 watt power
resistor at the air-conditioning equipment between terminals W and C
(non-heat pump applications only).
When using 4 wires (R,G,W,Y), the heating equipment
tries repeatedly to turn on, but cannot. At times the
display dims or disappears.
There is not enough power available. Connect a 270 ohm, 10 watt power
resistor at the air-conditioning equipment between terminals Y and C
(non-heat pump applications only).
When controlling a heat pump, heat comes on during
cooling cycle.
Configure thermostat for heat pump operation (Table 2, Step 3).
When calling for cooling, both heating and cooling are
energized.
The thermostat is configured for a heat pump. Configure the thermostat for
non-heat pump operation (Table 2, Step 3).
When controlling a commercial heat pump unit, unit
runsinreverseorheatingisalwayson.
Commercial heat pumps require that Heat Pump Option on thermostat is
turned OFF.
The thermostat temperature display rises to 99 F. There is not enough voltage to the thermostat. Check wiring and power
supply.
The resistor labeled “L3” on the thermostat is burned
out and brown. Thermostat will not work.
The thermostat has been wired incorrectly and the circuit board is burned
out. Thermostat must be replaced.
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1204
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