How to Troubleshoot Problems With Your Digital Thermostat

If you think you are having problems with a digital thermostat, there are a few simple tests that can be performed to isolate the problem and help you decide whether replacing the thermostat will solve the problem.

Tools Required:
  • Screwdriver
  • Digital Thermometer
Check Temperatures

Before getting too involved in the testing, check the room temperature on a digital thermometer. If the temperature matches what is being shown on the thermostat, you have at least verified the room temp sensor for the thermostat. Any discrepancy here indicates a bad thermostat sensor. While the sensor can probably be replaced, it is more cost and time effective to simply replace the entire unit. The next step will be to check the set point calibration.

Calibrate the Room Temp

Digital thermostats can be calibrated. This means that both the set point and room sensors are brought into balance. Since each thermostat is made differently, you will have to refer to the thermostat instruction manual in order to calibrate the unit correctly. If the manual is not available, call the manufacturer and ask to speak to a service technician, and that person can walk you through the simple process. Alternatively, some thermostats have directions for calibration printed inside the cover. Remove the cover and check before calling the manufacturer.

Check Thermostat Connections

If the sensors check out, the next step is to make sure that all of your connections are correct. Look for corroded wiring, wires that are not making a good connection, and places where a direct short may be impeding thermostat operation. If they are not already being used, put wire nuts on the tips of all wiring connections. many times, poorly connected wires will vibrate to an inactive state where they appear to be making a connection, but no power is able to travel through the circuit. It is important that all connections are tight, and that no stray strands may be contacting another wire.

Check the Thermostat

Typically, the wiring inside the thermostat is labeled R,W,Y,G,C. The R lead is usually the 24 volt main power supply for the thermostat, and the C lead is the common ground. Battery operated thermostats will not always have a (C)ommon ground. Disconnect all of the wires, and then connect the R wire to the W wire. The heating unit should turn on. Next, connect R to Y and G in turn, and verify that the Y turns on the cooling unit, and G activates the blower fan. When you are done with the testing, be sure to hook the wires back up the way they were when you started.

The Final Option

If you perform all of the simple tests listed here, and the thermostat still does not seem to function properly, the chance are very good that it is the thermostat itself that is faulty. Replacing it with a new thermostat will only take a few minutes of time, and may be the only option left if the other tests were all successful. Make sure that the replacement thermostat is the same general size and shape of the old one, and there won't be any problems changing it out.