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TH51 f OD NON-PROGRAMMABLE
THERMOSTAT
TROUBLESHOOTING
Table 5. Troubleshooting
Symptom
Possible
Cause
Action
Display is blank.
Thermostat is not powered.
Check for 24 Vac between Rc and C.
Check that fresh AAA alkaline batteries are
installed as marked on the battery holder.
Temperature settings do
The highest or lowest temperature
Temperature setting range:
not change,
setting was reached.
Heating:4O ° Fto 90 °F(4.5 °C to32 °C)
Cooling: 50 ° F to 99°F (10°C to 37°C)
Heating equipment failure.
Heat does not turn on
(Heat On is solid in the
display).
Cooling does not turn on
(Coot On is solid in the
display).
Loose or broken wire connection
between thermostat and heating
equipment.
Cooling equipment failure.
Check for 24 Vac at the equipment on the
secondary side of the transformer
between
power and common. If voltage is not
present, check the heating equipment to
find the cause of the problem.
Check for 24 Vac between the heat terminal
(W) and transformer
common. If 24 Vac is
present, the thermostat is functional. Check
the heating equipment to find the cause of
the problem.
Check for 24 Vac between the heat terminal
(W) and transformer
common. If voltage is
not present, check wire connection (loose or
broken) between the thermostat and the
heating equipment.
Check for 24 Vac at the equipment on the
secondary side of the transformer
between
power and common. If voltage is not
present, check the cooling equipment to find
the cause of the problem.
Check for 24 Vac between the cool terminal
(Y) and transformer common. If 24 Vac is
present, the thermostat is functional. Check
the cooling equipment to find the cause of
the problem.
Loose or broken wire connection
Check for 24 Vac between the cool terminal
between thermostat and cooling
(Y) and transformer common. If voltage is
equipment,
not present, check the wire connection
(loose or broken) between the thermostat
and the cooling equipment.
Fan does not turn on in a
Fan Control in Heating (Installer Setup
Set Fan Control in Heating (Installer Setup
call for heat (electric
Number 3) is set to Gas or Oil Furnace
Number 3) to Electric Furnace (Setting 1).
furnace).
(Setting 0).
Heat pump puts out cool
Changeover Valve (Installer Setup
Set Changeover Valve (installer Setup
air in the heat mode and
Number 2) is not configured to match the
Number 2) to match the changeover
warm air in the cool
changeover required by the installed
required by the installed heat pump.
mode.
heat pump.
Both the heating and
The heating equipment is not a heat
Set System Type (installer Setup Number 1)
cooling equipment are
pump but the System Type (installer
to match the installed heating and/or cooling
running at the same
Setup Number 1) is set to Heat Pump
equipment.
time.
(Setting 1).
Heating and cooling wires are shorted
Separate the shorted heating and cooling
together,
wires.
II
69-1712--I
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