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A furnace limit switch is a component of a forced-air furnace that is responsible for turning on the furnace blower once the desired heat has been met inside the furnace. Without a functioning furnace limit switch, a furnace would not be able to regulate the temperature in conjunction with a thermostat.
How do you know if a limit switch is bad?
The most common sign of a malfunctioning limit switch is the continuous operation of your furnace’s blower. Just as the limit switch won’t allow the fan to turn on until the warm air has reached the right temperature, the limit switch also shuts down when the air cools to a certain temperature.
What trips a limit switch on furnace?
If the air inside your furnace gets too hot, the limit switch trips to prevent overheating. If the furnace high limit switch trips due to overheating, there is likely an airflow issue that is preventing proper air movement through the system. A dirty filter is the most common cause of airflow issues.
Is my furnace limit switch bad?
One common symptom of a malfunctioning limit switch is a blower fan that doesn’t shut off. A bad switch also can prevent a furnace from operating at all. If the switch has completely failed and is stuck in the open circuit (off) position, the furnace won’t run.
How much does it cost to replace a limit switch?
You’ll need to get a limit switch from the same company that makes your furnace. This component could cost anywhere from $4 to $25, depending on your original equipment manufacturer.
Why do limit switches go bad?
Over time, your furnace’s limit switch can develop problems. When your furnace doesn’t have proper airflow, like when it is operating with a dirty filter, your heat exchanger will repeatedly overheat and put your limit switch through excess wear and tear. This can eventually cause it to malfunction.
What causes high limit switch on furnace?
The limit switch has two main components: a long temperature sensor located inside the furnace, and a switch mounting plate located on the outside of the furnace. One of the most common causes of high temperature limit switch failure is improper furnace maintenance, especially dirty air filters.
What is a limit switch?
A limit switch is an electromechanical device operated by a physical force applied to it by an object. Limit switches are used to detect the presence or absence of an object. These switches were originally used to define the limit of travel of an object, and as a result, they were named Limit Switch.
What causes a limit switch to open?
Limit switch codes The limit switch shuts off the burner when the temperature exceeds a preset temperature. When the temperature reduces to normal, the burner will come back on. The most common reason for limits to open is a plugged filter or a dirty blower wheel.
What does a tripped limit switch look like?
The most common way to tell if a limit switch is tripped is to observe the behavior of your furnace: Your furnace’s heating cycles end right after they begin. If the furnace won’t ignite, but the blower fan stays running, then the high limit switch might be tripped.
Can you bypass furnace limit switch?
Yes, you can bypass the high limit switch for testing.
Is limit switch a sensor?
Limit switches are a type of sensor that detect presence and absence. Specifically, mechanical limit switches are switches that are mechanically activated, meaning that they have some sort of arm, lever, knob, plunger, etc., which is physically—or mechanically—activated by making contact with another object.
What is an example of a limit switch?
A good example of this is an automatic garage door. Without a limit switch that stops the door when it reaches the bottom rail, the door would keep moving downwards and eventually crash into the ground, causing serious damage. Limit switches can also be used as part of a larger control system.
Should a limit switch be open or closed?
The limit switch is a normally closed switch in series with the sail switch and the thermostat. Being temperature actuated, it is designed to “snap open” when an over temperature condition occurs. Thus the switch is normally opening under full load conditions and that causes arcing of the contacts.
How do you reset the limit switch on a Trane furnace?
To access it, you’ll need to remove the front panel of the furnace. You may find that many models have limit switches where the reset button is located. The button is often located on top of the switch and will need to be pressed to initiate the reset.
What is the difference between micro switch and limit switch?
Do you know there is really a micro switch within the limit switch. The distinction between both is the limit switch includes a solid casing, and in which it comes in contact with the item, there’s a buffer space that’s retracted by means of a spring. Due to the buffer space, the micro switch is shielded.
Which type of switch is limit switch?
What is a limit switch? Limit switches come in many forms and functions but at their most basic definition, they are an electromechanical switch that operates based on the movement or presence of an object. While it is not an electrical switch, your toilet float valve is quite similar to a limit switch.
Where is the limit switch located on a gas furnace?
The limit switch is a safety control switch located on the furnace just below the plenum. If the plenum gets too hot, the limit switch shuts off the burner. It also shuts off the blower when the temperature drops to a certain level after the burner has shut off.
