Does Your Furnace Have A Bad Limit Switch?

Furnaces get pretty hot when they are functioning. In order to keep you safe and prevent fires, furnace manufacturers build in several safeguards. One of these is a limit switch. The limit switch is meant to turn the blower on when the furnace itself reaches a certain temperature. It also turns the furnace off if the temperature grows to a dangerous level. A functional limit switch is important for furnace operation and overall safety. But what if your limit switch fails? This is actually a pretty common problem and one that HVAC techs can repair. Learn more below.

How do you know your limit switch is broken?

If your furnace is not turning on at all, this could be because the limit switch is broken. However, there are usually earlier signs of limit switch breakdown before the switch fails completely.

The first issue you might notice is short-cycling. In other words, the furnace will turn on and run for a minute or two, then turn off again, and then turn on again. The home will still get warm, but the furnace won't run for more than a few minutes at a time. This happens because the limit switch "thinks" the furnace is over-temperature and turns it off prematurely.

Another sign of limit switch issues is if your furnace takes a long time to start blowing air after you hear it kick on. This happens because the limit switch is not accurately detecting when the burner has reached temperature and is turning the blower on late.

How is a broken limit switch repaired?

Your furnace repair tech should be able to tell rather quickly if a broken limit switch is the cause of your furnace issues. They can then replace the limit switch. This is a relatively inexpensive part to buy, and most furnace repair companies keep a few on hand since it's such a common repair. However, if you have a less-common furnace model, your HVAC tech may need to order your new limit switch and it might take a couple of days to arrive.

Replacing the limit switch is usually worth it unless your furnace is already old and has other, competing issues. 

As your furnace ages, keep an eye out for signs that the limit switch is becoming temperamental. If you do notice signs of a problem, it's important to have the switch repaired promptly before you experience a total loss of heat.

For more information on furnace repair, contact a company near you.