Testing the Programmable Zone Sensor (PZS)
1. Verify unit operation by running the unit through test mode.
2. Verify that the PZS has a normal display of time, temperature, fan, and system status.
3. ReliaTel™l controls, disconnect wires from J6-11 and J6-12. Measure the dc voltage
between terminals 11 and 12. Voltage should read between 28 to 32 Vdc.
4. Reconnect wires to terminals 11 and 12. Measure the voltage between 11 and 12 again. Voltage
should flash at a 0.5-second rate, with a voltage value randomly changing from approximately 24 to 32
Vdc.
5. On the PZS, press the FAN button to turn the fan ON. If the fan comes on, the PZS is good; if the fan
does not come on, the PZS may be defective and will need to be replaced.
Note: The sensor will not communicate if the wrong baud rate is selected. The PZS is shipped with the baud rate set to 1200. See the options menu setup in the literature to verify the proper baud rate. The baud rate may need to be changed to 1024 for units built before 1/96.
Because the PZS is a communicating sensor, troubleshooting is very limited. Step 2 through Step 5 of testing the sensor are the first steps to verify. The following table will provide other troubleshooting tips
for diagnosing the sensor and unit operations. If all wiring and preliminary tests do not indicate any
defects, disconnect the PZS from the wall and take it to the unit, and with a short (approx. two feet) length of thermostat wire, connect the PZS and see if symptoms still exist. If not, check for thermostat wire routing in close proximity to high voltage wires and fluorescent lights.
| Symptom | Probable cause and solution |
| Display does not come on | Check for 24Vac on terminals 11 and 12 of the sensor |
| No communication with unit | Verify a varying voltage per step 2 of testing the sensor. If no voltage is present, check the wiring to the unit |
| The sensor is communicating, but the unit won’t run | Check option 18 in Option Menu setup for correct baud rate |
| The displayed zone temperature is different from the actual temperature | Follow the Option Menu setup in the literature to calibrate the display |
| Zone temperature is not displayed | Check option selection in option menu setup |
| Displayed zone temperature reads “99” | Space temperature is above or below the measurable range of the sensor |
| Displayed zone temperature reads “Sh” and the COOL FAIL icon is illuminated | Verify that option 11 in option Menu is set correctly. If correct, check the wiring from the remote sensor at terminals S1 and S2 for a shorted condition |
| Displayed zone temperature reads “oP” and the COOL FAIL icon is illuminated | Verify that option 11 in option Menu is set correctly. If correct, check remote sensor wiring at terminals S1 and S2 for an open circuit condition |
| Programmable sensor will not respond to keypad selections | Check the lower-left corner of the display for a padlock icon. If displayed, press and hold the Time (+) and (-) key until the icon goes away |
| Fan mode is set to on but does not run during unoccupied mode periods | Check option 6 in option menu setup for Auto selection during unoccupied |
| Buzzer indicates System Failure, Check filter or service is required | Press erase key to reset the filter lapse timer. The buzzer will be reset until noon of the next day if a system failure has not been corrected |
| Sensor will not hold override changes | Press the HOLD TEMP button within 20 seconds after changes are made |
| COOL FAIL flashes and the unit doesn’t run. Check for varying the voltage on terminals |
Sensor not communicating with the unit. 11 and 12 at the unit. If voltage is steady at approximately 30 Vdc, check for an open circuit in wiring |
| COOL FAIL + HEAT FAIL icons flash simultaneously | Check for defective outside air sensor. Emergency input is open. (RTRM version 4.0) Coil Temp Sensor fail (HP) |
| HEAT FAIL flashing | A heat failure has occurred. If HP unit, the unit may be in emergency heat, or there is a defrost problem |
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.