- Locate your furnace's heating duct. …
- Locate the white limit switch. …
- Look at each arm to identify the settings. …
- Identify the component (setting) located in between the two arms. …
- Set the temperature on the middle component to approximately 105 to 115 degrees Fahrenheit.
How do you manually reset a limit switch?
- Locate your furnace's heating duct. …
- Locate the white limit switch. …
- Look at each arm to identify the settings. …
- Identify the component (setting) located in between the two arms. …
- Set the temperature on the middle component to approximately 105 to 115 degrees Fahrenheit.
What causes a high limit switch to trip?
If the supply air is too hot, the
interior of the furnace overheats
, which can cause damage to components. The limit switch trips when temperatures are too hot, effectively shutting down the system and locking furnace operation until the unit cools.
The High Limit Reset Button is located
behind the gas valve
.
How do I know if my limit switch is bad on my furnace?
With the furnace in full operation, connect a digital voltmeter across the two connections of the limit switch. The voltage drop should be less than or a maximum of 0.1 VDC. The switch should be
immediately suspect if the voltage drop is 0.2 VDC or higher
(Fig. 1 indicates a bad limit switch).
Why is my furnace going off on high limit?
In a gas furnace, a high-limit,
switch turns the unit off if air doesn't ventilate from the exhaust flue properly
. … A high-limit switch will turn a furnace off if it becomes too hot or is obstructed. Changing the furnace's air filter and cleaning the blower motor may help the switch perform better.
If you have a gas or oil furnace, the reset button
may trip if you are out of fuel
. … If a furnace isn't receiving enough airflow, it may overheat and trigger the reset button to trip. Make sure to clean or replace the air filters and keep the air vents open enough for proper airflow.
Can you bypass a limit switch?
1 Answer.
Yes
, you can bypass the high limit switch for testing. It's as trivial to do as it sounds.
How do I test a limit switch?
The switch should be immediately suspect if
the voltage drop is 0.2 VDC or higher
(Fig. 1 indicates a bad limit switch). Verify that your ohmmeter will read “0” when the two leads are shorted together. The meter should read between “0” and “0.1” Ohms.
Where is the high limit switch on my furnace?
The high limit switch is usually
attached to a metal plate
, which is bolted to the outside of the furnace plenum (the large metal box where air is heated.) You will have to remove the furnace cover to find it.
Can I bypass the limit switch on my furnace?
There is no good reason for a consumer to bypass
a furnace limit switch. Furnace switches are reliable, inexpensive to replace, and are designed for protection of the consumer. Bypassing a furnace limit switch or any home heating component can create dangerous safety and fire hazards.
What does a furnace limit control switch do?
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 much does it cost to replace a limit switch?
Another safety control is a high limit switch, which measures the temperature of the furnace to ensure it is running within safe temperatures. Both of these are small but critical parts for safe furnace operation, and they will run from
$150 to $400
to repair.
Can a dirty air filter cause furnace to shut off?
In the most severe cases, a dirty furnace air filter
may cause damage to the internal components of the furnace
. If the furnace isn't able to turn on, this is an indicator of damage to the fan, pilot light, heat exchanger, pressure switches, gas valves, or other components.
How do I fix my furnace from overheating?
- Check your vents. Vents can be blocked by furniture and other objects, which restrict air flow and can potentially lead to overheating. …
- Change your air filter. …
- Inspect your furnace's evaporator coil. …
- Check your furnace's blower fan.
Can a bad thermostat cause a furnace to short cycle?
A faulty thermostat can
be a possible culprit for short cycling. If you're experiencing a furnace short cycling, the first and easy thing you can do is check your thermostat to see if it's performing correctly. Many times, a homeowner may forget to switch their thermostat over to the heating mode.
