Troubleshooting Guide
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Troubleshooting Guide

Remote Sensor Troubleshooting Guide (F145-1049 and F145-1170)

When installing a remote sensor, be sure that the proper jumper on the back of the thermostat (not the subbase), has been clipped and the ends separated, as pictured in the installation instructions for the remote sensor. On Comfort-Set II (-71) single stage models, clip jumper wire W-22; on Comfort-Set II (-71) multistage and heat pump models, clip jumper wire W-18.

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To function correctly and read temperature accurately, the thermostat (when using a remote) must have constant 24 volt power. If the thermostat temperature is steadily dropping, reading low, or reads 08° when a remote sensor is installed, it can be traced to one of the three following conditions.

Condition

Test

Comments

1. Loss of 24 volt power. Remove the batteries and re-install thermostat. If display goes blank, check heating and cooling system to determine why 24 volt power is absent. For the sensor to read correctly, the 24 volt system power must be present. Some systems may require an isolation relay to provide constant power to the thermostat. Limit or safety devices in the equipment can also cause a power interruption.      
2. A broken wire on S1, S2 and S3 from the thermostat to the remote. Disconnect sensor wires at thermostat. Attach a short piece (2’) of three wire conductor thermostat wire to S1, S2 and S3 on the sub-base. Bring the remote sensor to the thermostat location and attach S1, S2 and S3 respectively. Reattach thermostat. If the temperature begins to climb (slowly), it is reading correctly. If it reads correctly with the 2’ length but improperly when attached to the wire run, there may be a fault in the wire run. Repair or replace the 3 wire shielded cable. Also be sure the remote wire run is not parallel to line voltage wires that carry heavy inductive loads, or across fluorescent light ballasts that may cause an inductance to be transmitted to the thermostat.
3. A shorted or damaged remote sensor. If you have tested 1 & 2 above and the temperature stays at or near 08°, it indicates a shorted or damaged remote sensor. Replace remote sensor.

Installation note:
When you clip the jumper lead (W-18 or W-22) on the thermostat to add a remote sensor, it disables the thermostats temperature sensor. This causes the room temperature display to start dropping very slowly until the remote sensor is installed and the power is restored. It is possible for the room temperature to read as low as 08°. Digital thermostats and remote sensors acclimate very slowly to temperature change. It may take an hour or more for the temperature to acclimate to the room temperature. As a general rule, if the temperature is dropping (well beyond the actual room temp), one of the conditions in the chart above has occurred. If the temperature is climbing, it will eventually reach room temperature and read correctly. To expedite the rise in temperature from 08, remove the batteries for five minutes and allow the thermostat to default to factory settings.