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.Click to see full answer. Also question is, what does a limit switch look like?A limit switch is a device that’s located under your furnace’s supply plenum. It reads the temperature of the plenum and waits until it gets appropriately warm. 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.Furthermore, what does high limit switch do? A high-limit switch is a protective part of a furnace designed to keep the mechanism from overheating itself. A furnace is at a risk of overheating any time airflow is limited from passing through the heat exchanger. The high limit switch shuts down the furnace at a set limit so a clog doesn’t burn out the system. what does high limit switch open mean? 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 shuts off the burner when the temperature exceeds a preset temperature. When the temperature reduces to normal, the burner will come back on.What causes a limit switch to go bad? Common Problems with Limit Switches Like other components in your heating system, the limit switch can malfunction. For example, if the air flow in your system is significantly reduced by a clogged air filter, there won’t be enough air circulating through the system; this can cause the heat exchanger to get too hot.