Q:

How can I tell if a thermostat is bad?

A:

Quick Answer

Thermostats tell your system how and when to change the temperature. They come in different makes and models, but the initial troubleshooting steps are the same for all thermostats. You need a soft brush, compressed air and a screwdriver.

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Full Answer

  1. Check the circuit breaker

    Make sure you have not tripped a switch or blown a fuse, and reset if needed. Confirm the power is on at the furnace. Call a certified technician if you are unsure what to do, or if things appear to be unsafe.

  2. Start at the source

    Replace the battery in your digital thermostat if there is no display. For an analog low-voltage model, make sure the unit is level and flush to the wall. If this doesn't fix the problem, gently pry off the cover, and clean the inside using a soft brush or compressed air. Visually inspect the components; replace loose wires and tighten terminal point connections. Never touch wires if you are unsure of voltage.

  3. Clean the bimetallic coil in analog models without a mercury ampoule

    Turn the thermostat to the lowest setting; clean the bimetallic coil with compressed air or a soft brush, repeat for the highest setting. Return the thermostat to your desired temperature.

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Related Questions

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    How does a thermostat control ambient temperature?

    A:

    Thermostats control ambient temperature by sensing the temperature in a room and responding to that by activating heating or cooling equipment or remaining dormant. Most modern home thermostats rely on a bimetallic strip to determine the current temperature at or near the thermostat's housing.

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    What is the function of a high temperature limit on a thermostat?

    A:

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    Where can you find a programmable thermostat for an HVAC system?

    A:

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    How does a thermostat work?

    A:

    Generally speaking, thermostats work by using a mercury switch that is in contact with a thermometer wire to trigger a temperature-adjustment lever in response to the expansion or contraction of the wires as they are heated or cooled. The expansion and contraction of these wires triggers switch relays that control heating and cooling by triggering either a circulation fan and heater or air conditioner.

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