Why Does My Heater Keep Running After It Has Reached The Set Temperature?

It could be a thermostat issue or air filter blockage. Both of these can cause the heater to run even after reaching the set temperature. However, it could also be something completely different – such as the blower system.

Whichever the case, most of these issues are easy to repair as it’s often a lack of communication between various components of the AC. You’d be in greater trouble if the heater keeps running without reaching the set temperature.

Dangers and Costs

Perhaps we should begin by discussing why you should be worried if your heater continues to run without stopping even after reaching the set temperature.

Excessive indoor warmth

Although we want a warm home in winter, this doesn’t mean we want the place sweltering hot. We still want it comfortable. In many cases, anything around 70˚F is good enough. Depending on your needs, you may want it slightly lower or a tad higher. But not 90˚F warm. Unfortunately, that’s where you’d be headed if the heater keeps running even after reaching the set temperature.

Arid indoor conditions

 Winter months are relatively dry compared to the rest of the year. It’s why all respiratory issues, including allergies and the flu, are most common in winter. Heating often makes the situation worse because the heating process uses up moisture. Now, imagine a situation where the heater keeps running even after reaching the set temperature! It can feel like a day in hell.

Faster wear and tear

Every second that the heater is on, the moving parts keep grinding against each other and other parts of the heater. The fan will keep rotating and, in heat pumps, the rotary motor keeps rotating. It’s a process that causes natural wear and tear. The longer the system runs, the greater the wear and tear- it doesn’t matter if the unit has reached the set temperature.

High power bills

Finally, if your heater keeps running even after reaching the set temperature, you should prepare for a hefty power bill. The amount you’ll ultimately pay depends on the heater’s power rating and electricity prices in your area. It also depends on how long the problem persists. However, don’t be surprised if your monthly power bill is double the usual rate.

4 Reasons Why your Heater Reaches Temp but Keeps Running

If you’re noticing the problem for the first time, understanding the potential cause can help resolve the issue without involving an HVAC technician.

Or even if you ultimately have to call the technician, at least you’d know what’s needed for the repairs and the likely labor costs.

The four most common reasons why a heating system, especially furnaces and heat pumps, can continue to run even after reaching the set temperature are as follows;

1. Thermostat Issues

The most common issue is wrong thermostat settings. If you set the thermostat too high, then the heater will continue to run even when you’ve achieved the desired heating levels.

For instance, if the thermostat is set to 75˚F, it will work hard to achieve that temperature – no matter how long it has to run. As a result, you may feel warm enough (most people do at 68˚F to 72˚F) but find that the heater is still running.

If it’s not the setting, then perhaps the thermostat is broken, or something is amiss. Perhaps the batteries are dead? Or maybe a few wires have come off?

Solution: Begin by making sure that the thermostat is set to “Heat” mode. Then, check that the temperature setting is between 68˚F and 72˚F as the Department of Energy recommended. If the problem persists, it could be wiring issues. Call your HVAC technician.

2. Fan Issues

Aside from the thermostat, the unit may also run continuously because the fan is set incorrectly. In most cases, the blower fan on a heater has two settings – ON and AUTO. When you set the fan to the ON setting, it keeps running no matter what until you shut it off. It will continue to run even after the set temperature is reached.

Indeed, sometimes the heater may cycle off, but the fan will keep running until you shut it off at the AC or from the remote.

Solution: If you want the fan to run only when the heater is ON, set it to AUTO mode. It will go off as soon as the heater goes off.

3. Dirty, Clogged Filters

Dirty filters can cause all sorts of problems in your heater. Among them, you may find that the heater keeps running without stop. What usually happens is that a blocked filter constricts airflow through the heater.

Different manufacturers position the filters differently. However, in most configurations, there’s at least one filter on the return end. If the filter is clogged, it won’t allow cold air to enter the AC.

The result is that you may have very little warm air coming out of the supply side. This keeps the heater constantly running as it makes it more difficult to achieve and maintain the desired temperature.

Solution: You can avoid dirty filter issues in the first place by ensuring regular maintenance. Clean the filter at least once every two weeks and replace it every 1-2 months.

4. Leaky Ducts

Finally, the reason your heater seems to run nonstop even after reaching the set temperature could be a leak in the ductwork. When there’s a leak in your ductwork, the unit loses valuable heating power, meaning that it takes a little longer to reach the desired temperature and may also struggle to maintain the said temperature.

So, even after reaching the thermostat setting, it will continue to run to maintain the setting – the bigger the leak, the worse the problem.

Solution: Duct leaks are a little complicated to diagnose and fix. If you can do it yourself, well and good. Otherwise, call an HVAC professional.

Key Takeaway

If your heater keeps running even after reaching the set temperature, it’s likely a thermostat issue, an issue with the fan, a blocked filter, or leaking ductwork. Fortunately, all four issues can be addressed with ease by a licensed professional.