Green Leaf Air

by Rifat A. in Blog, HVAC Repair & Maintenance, HVAC Tips 0 comment

The furnace requires about 15 minutes to reach your desired temperature. But if your furnace stops right after you turn on the switch, it’s probably happening because of some furnace blower motor malfunction.


4 Reasons Why Your Furnace Blower Starts & Then Stops Immediately

1.  Faulty Flame Sensor

The main function of the flame sensor is to recognize if the flame is burning inside the furnace combustion chamber or not. When it doesn’t recognize the flame burning, it turns off the furnace. However, when the flame sensor is dirty, it won’t be able to recognize the burning flame inside the combustion chamber. As a result, it will turn off the furnace even when there is enough fuel in the furnace.

If you haven’t cleaned your furnace in months, chances are the flame sensor is covered with dust. While cleaning the flame sensor, it’s advised to use fine-grade sandpaper or an abrasive pad. However, while cleaning the flame sensor, you shouldn’t put excess pressure on it. Otherwise, you’ll end up damaging the flame sensor and make the situation worse.

2.  Malfunctioning High Limit Switch

The high limit switch is also known as the limit, and it works as a safety switch. When the furnace’s internal temperature goes beyond the usual temperature, the high limit switch turns off the gas valve and burner, protecting the furnace from overheating.

When you have a malfunctioning high limit switch in your furnace, it’ll automatically turn off the furnace blower motor. To check if the limit switch is in good condition or not, you should call a heating professional. A heating professional will easily be able to identify a malfunctioning high limit switch and replace it.

However, you can replace the high limit switch by yourself. Besides, this high limit switch doesn’t cost much.

3.  Faulty Hot Surface Ignitor

When you turn on the furnace, this surface ignitor rises up to 2500 degrees Fahrenheit and lights the fuel. But when the hot surface ignitor doesn’t function properly, your furnace will stop suddenly.

Generally, a furnace surface ignitor lasts around seven years. After that, it starts cracking and cannot light the fuel properly.

To check the condition of the furnace surface ignitor, you can remove the panel of the furnace or use the multimeter. While checking the surface ignitor, if you notice that the ignitor is glowing up right after you turn on the furnace, your surface ignitor is in good condition. But if the surface ignitor doesn’t glow or heat up when you turn on the furnace, you have a faulty furnace surface ignitor.

If your furnace is very old or has a faulty hot surface ignitor, it’s advised to replace the surface ignitor.

Again, over time, the furnace surface ignitor can become dirty and cause problems while turning on the furnace. To clean the ignitor, at first, remove the ignitor by unscrewing it and then use an Emery cloth to clean the ignitor.

4.  Thermostat Issue

The placement of the furnace thermostat is crucial to get the most out of the furnace. If you have installed the thermostat where it gets direct sunlight or near any heat-generating appliances, the thermostat will receive the wrong information about the house temperature. As a result, it’ll turn off the furnace before the house is warmed.

If this is the case for you, you should move your thermostat to a place where it can accurately read the temperature of your house. To know the exact place, contact a heating professional and install the thermostat accordingly.

Apart from this, if there is a thermostat wiring problem, your furnace will quickly turn off. In this case, you’ll have to check if the thermostat wiring is in good condition or not.

Sometimes, when the thermostat batteries are dead or require replacement, your furnace can turn off quickly. Here, replacing the thermostat batteries will solve this HVAC concern.



if you’re currently using a manual thermostat, switch to a programmable or smart thermostat. To learn more, check our previous blog about Manual, Smart or Programmable Thermostat: Which One is Better?


For any kind of HVAC support, repair, and replacement, contact Green Leaf Air. We provide our HVAC services in Dallas and its surrounding areas 24/7.


See the summary of this content here in this infographic – 4 Reasons Furnace Blower Starts & Stops Frequently [Infographic]


How to Replace Furnace Blower Motor
How to Replace Furnace Blower Motor
Rifat A.

HVAC Expert, Author & Mathematician... rifatahmed.com

0 thoughts on “How to Fix: Furnace Blower Starts & Then Stops Immediately”

Leave a Reply