Troubleshooting Common Thermostat Problems
Contents
1. It should always be set to No Voltage outputs To check your voltage outputs you must have a load on the thermostat outputs and measure between R and the specific output Your readings should be between 0 5 volts and 1 1 volts AC if the output is on and between 21 and 30 volts if off Also you cannot read temperature from a remote sensor using an ohmmeter Dry Contacts When CK1 and CK2 are energized the thermostat is forced into Occupied 1 if the stat is in Program On mode in any other mode the dry contact is ignored When CK1 and CK2 are de energized the thermostat will revert to its regular program On the 33CS071 01 and the P374 2100 operation of the CK1 and CK2 terminals is configurable to normally open or normally closed and operates in all modes except OFF Ck1 and Ck2 Programmable stats only works if the Thermostat is in Program On mode Non programmable stats works in all modes except OFF Resistor The resistor that is included with the thermostat should ONLY be used if there is no common wire AND the thermostat is not operating correctly see number 2 in troubleshooting Otherwise the resistor is NOT USED2. 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 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 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 9 Buttons don t work most likely the keypad is locked Press Mode Up and Down simultaneously to unlock the buttons 10 Temperature inaccurate Calibrate the thermostat On 4 button models press Mode and Down for two seconds the
3. 1 2 3 4 5 6 7 8 9 1 1 1 0 1 2 13 Troubleshooting Common Thermostat Problems Signature Star Series Except for P374 0000 0100 0200 0300 Clock losing time Display goes blank or shows PF when starting cooling or heating Unit running backwards cooling on heat demand heating on cool demand Unit runs both heat and cool at the same time Display blanks out during heating Wireless thermostat won t turn on heat or cool Batteries die rapidly in wireless stat Setup can t get into advanced setup or can t get past step 2 Buttons don t work Temperature inaccurate Fan doesn t come on with the heat Thermostat settings change or scramble when supplemental heat comes on 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 h
4. owever many minutes the power was off to the thermostat Correction Find the cause of the high temperatures dirty filter etc 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 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 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 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 Wireless
5. r these are digital sensors not thermistors and they can be damaged by an ohmmeter 14 Thermostat doesn t respond to changes in room temperature this happens when there is air blowing through the thermostat from the wall behind it Insulate the hole behind the thermostat with insulation spray foam or even duct tape whatever will stop the airflow from behind the wall 15 Erratic operation partial display or fluctuating temperature This can be caused by poor pin connections between the backplate and the thermostat almost always because the backplate is flexed against an uneven wall Loosen the screws that attach the backplate to the wall allowing the backplate to flatten out then snap thermostat back onto the backplate 16 Switches won t move or door won t close properly this is a mechanical problem caused by tightening the backplate screws too tight on a non flat wall which warps the backplate Loosen the mounting screws to allow the backplate to straighten out General Tips Wireless thermostats Make sure the model number of the thermostat matches the model number of the receiver i e P474 1100RF goes with P474 1100REC not with P474 2300REC If the model numbers do not match the stat and receiver will not be compatible When replacing a Venstar T100RC with a Totaline wireless stat you must replace the receiver with a Totaline as well Also at this time the Zone setting in wireless thermostat setup is not used
6. whole display will light up Press Mode and the room temperature will appear Use the Up or Down buttons to adjust the temperature Press Mode to exit On 8 button models with a door hold Mode and Fan for 5 seconds the whole display will light up Press Up and Down simultaneously once then again Room temperature will appear Use Up or Down to adjust temperature press Mode to exit 11 Fan doesn t come on with the heat Turn electric heat on setup step 5 12 Thermostat settings change or scramble when supplemental heat comes on Some heat pumps create a large voltage spike when the unit goes in to defrost and or when the supplemental heat comes on This large voltage spike can cause the microchip in the thermostat to reset changing settings Settings can be restored with a factory reset see below but if the problem is re occurring replace the thermostat with a flush mount model a P474 1050 2050 or 2150 a 33CSSP2 WC or with a newer Signature or Debonair with a date code later than 1499 all of which have additional high voltage protection 13 Remote sensors don t show correct temperature Check that the degree symbol on the thermostat is flashing if it is not flashing the remote sensor is not connected correctly Check wiring and make sure that you are not using shielded wire as this will throw temperature off Do not reverse RS 5 and RS GND as this may damage the sensor Note Do not use an ohmmeter to test the senso
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