Why Is Your Heater Not Working When Your Thermostat Is On?

It was bitter cold overnight so you got up very early and turned up the thermostat so your kids wouldn’t see their breath when it was time to get ready for school. You heard everything working like usual but when everyone got up, it was still cold in the house. What gives? You’ve checked the furnace filter, switches, and wiring, and the thermostat works but there’s still no heat. The heater motor is even running fine but with no warmth to be found.

Let’s look at some common culprits keeping your house in a frigid state.

Technical glitches at work

All furnaces manufactured from the start of the 2000s include a safety switch to prevent active heating or air conditioning in the midst of a technical problem. If a potential hazard is sensed by the unit, the furnace’s heater won’t kick in regardless of how high you turn up the thermostat. Issues creating this problem include dirty evaporator coils, clogged air filters, broken wiring, malfunctioning circuit board or a dead blower motor.

In any of these cases, it is always best to enlist the help of a professional.

Malfunctioning fuel source

Your furnace system requires gas, electricity, and sometimes water in order to properly function. The first thing to check is the circuit breaker and if that is fine, the furnace might be struggling to take in enough gas. This can be caused by a stuck valve or a defunct control board that is not communicating the correct signals to start the heater. The heater cannot create flame without fuel, so check for stuck valves or other impediments.

Furnace needs some love

If your furnace is humming along nicely but then heating stops intermittently or altogether, there is likely a maintenance problem. Regular and thorough furnace maintenance is critical and yet many homeowners underestimate this need or simply ignore it. Built-up residue and debris inhibits a furnace’s efficiency and heating performance and causes related problems such as resistance in the motor, burners using too much gas, undue stress on the motor and power source, and other issues.

Faulty thermostat wiring

In some cases, damaged or old wiring, accumulated dust or dramatic temperature changes can put your thermostat on the fritz and prevent it from properly communicating with the furnace heating system. This will cause the furnace to stop producing heat altogether, emit erratic heat, or cycle on and off far more than is necessary.