As a working example we examine the honeywell combination fan and limit control type l4064b.
Furnace high limit switch troubleshooting.
What happens if your furnace limit switch stops working properly.
If the high limit switch was bad the furnace should not fire.
Depending on your furnace model the switch will be surrounded by a silver or white cover.
Over time your furnace s limit switch can develop problems.
Locate the white limit switch.
Some furnaces provide extra safety features by wiring two or three high limit switches in a series that check the temperature in the furnace at different points.
Limit switches turn off the burner and turn on the circulating fan if there is a high temperature condition in the furnace.
So to put it simply the limit switch tells the furnace fan when to turn on and when to shut off and it tells the furnace to shut down if it is overheating.
High limit switch a high limit control switch will turn off the gas to a furnace if the temperature becomes too high.
It s also known as a fan limit switch or simply a limit switch.
When the high limit switch trips the flame heating element will be shut off and the blower will continue to run to clear the heat.
If the temperature inside of the plenum gets too hot it shuts off the gas supply to your burners to prevent your furnace and heat exchanger from overheating.
The switch makes sure the furnace is operating safely and at its desired settings.
The blower will continue to run until either the system is reset or the limit switch closes.
Remove the cover by lifting it upwards or pulling it off to reveal the body of the switch and two metal arms.
A limit switch also acts as a safety device for your furnace.
The high temperature limit switch is an important device used in forced air furnaces powered by gas or heating oil.
As a safety the high limit.
For example if the blower motor stopped running then no air would move through the unit.
If the furnace failure code indicates an open limit or open high temperature switch or open rollout switch it is probable that the furnace has overheated.
The limit switch is a safety switch that monitors t.
The flames would raise the temperature inside the unit and have no place to go getting hotter and hotter.
