Troubleshooting Common Thermostat Problems
Signature/Star Series
(Except for P374-0000, 0100, 0200, 0300)
1) Clock losing time
2) Display goes blank or shows “PF” when starting cooling or heating
3) Unit running backwards – cooling on heat demand, heating on cool demand
4) Unit runs both heat and cool at the same time
5) Display blanks out during heating
6) Wireless thermostat won’t turn on heat or cool
7) Batteries die rapidly in wireless stat
8) Setup – can’t get into advanced setup or can’t get past step 2
9) Buttons
don’t
work
10) Temperature inaccurate
11) Fan doesn’t come on with the heat
12) Thermostat settings change or scramble when supplemental heat comes on
13) Remote sensors show wrong temperature
14) Thermostat doesn’t respond to changes in room temperature
15) Erratic operation, partial display, or fluctuating temperature
16) Switches won’t move, or door won’t close properly
1) Clock losing time
This almost always caused by the furnace tripping on high temperature limit, or some other safety limit.
When the temperature limit is exceeded, the furnace shuts off the burners and the 24VAC to the
thermostat. When the stat loses power, the clock stops. The furnace blower remains on, so the
homeowner may never notice a problem, and when the temperature is back within limits, the burners
come back on, and the power to the stat is restored. The clock will be slow by however many minutes
the power was off to the thermostat. Correction: Find the cause of the high temperatures – dirty filter,
etc.
2)
Display goes blank or shows “PF” when starting cooling or heating
– The thermostat only does
this when there is no common wire. If the common wire is present, check it for continuity, look for a
short, a broken wire, or a bad connection. If the equipment is a heat pump, or heat only or cool only,
you MUST have a common wire. If the equipment is gas/electric, the stat will work without a common,
but if it goes blank when starting the heat or cool, add the resistor (included with the thermostat) at the
equipment side (not at the thermostat!) between W and C.
3)
Unit running backwards
– cooling on heat demand, heating on cool demand – the heat pump setting
is wrong – go to setup step 3 and change the heat pump setting. If the unit is a commercial heat pump,
it may not require a heat pump thermostat, so step 3 should be turned OFF. In this case, electric heat
(setup step 5) may have to be turned ON.
4)
Unit runs both heat and cool at the same time
– the heat pump setting is wrong – go to setup step 3
and turn HP to OFF.
5)
Display goes blank during heating
– most likely the furnace is tripping on high limit or some other
safety limit. The furnace will shut off the burners AND break the R leg to the thermostat, so the
thermostat has no power and will go blank. Solution – identify the cause of the limit trips.
6)
Wireless thermostat won’t turn on heat or cool
– check the house code on the thermostat and on
the receiver. They must match. The house code on the receiver is set using dip switches, the house
code on the thermostat is set in the thermostat setup, step 4. Check setup step 3 (zoning), it should be
always be set to no. Also, check batteries – these thermostats require AA Lithium batteries, alkalines
will not work correctly.
7)
Batteries die rapidly in wireless stat
– make sure the batteries are AA Lithium batteries. Regular
alkaline batteries will die rapidly and cause erratic thermostat operation. Also check the thermostat
backlight setting in setup step 9. If the backlight is ON, the batteries will run down very rapidly. If the
customer really wants the backlight on all the time, use the optional transformer part # P474-0800 to
plug the thermostat into a wall outlet.
8)
Setup – can’t get into advanced setup or can’t get past step 2
– to get into setup on any of the 4
button thermostats, hold Mode and Fan (or Mode and Override) for
SEVEN
seconds. If you only hold
the buttons two seconds, you can only get to step two. You must hold the buttons SEVEN seconds,
even though the display will say setup after two seconds.
