How to Diagnose Thermostat Problems

Check the settings on your thermostat and make sure that it is turned on. If it is a wireless system, you may need to replace the AA lithium batteries. If your thermostat is plugged into the electrical system on your house, make sure that the breaker has not been flipped or broken. If the breaker continues to flip from an overloaded circuit, you will need to contact an electrician to help fix the problem.

Unscrew the thermostat housing and inspect the metallic needle if it is an older thermostat model. You may need to pop off the covering by gently prying it with your screwdriver. Use a soft brush to clean the interior of the thermostat housing and the metal contacts inside the unit.

Use a multimeter to check for continuity in the wiring that is proceeding from the thermostat's transformer. Set the multimeter to measure for infinite resistance. Touch the probes to the exposed wiring joints or solders. If the multimeter measures the resistance at infinity, then part of the circuitry within the thermostat is faulty. Remove the thermostat completely and inspect the wiring for any broken, frayed or burnt components.

Check the air filters in your home if the furnace is not putting out a strong flow of hot or cold air. If the filters are clogged or have too much debris on them, then they will impede the flow of air into your ductwork. Clean filters will improve the quality of air as well as save you money by not forcing your system to work as hard to keep up with the temperature regulation demands.

Put your hand near a vent to check the temperature of the air that is coming out. If the air is not coming out as forcefully as it used to, then your problem may not be your thermostat. Use a tissue paper placed near your vents to check for dust coming out from your system. If the tissue paper becomes dirty, then your ducts may need cleaning.

Turn your thermostat off and allow for it to sit for two to three hours if your are using your air conditioning system. If the coils are frozen, then the unit will not be able to transfer the heat from the air within your home. If your air is clean and it still does not blow out forcefully, then you may have a leak or tear in your ductwork. Search for which vents are working in order to help figure out which ducts need maintenance, which can be done with duct-tape.