Open the access panel and locate the high limit switch.
Atwood furnace limit switch test.
The limit switch is a simple temperature controlled switch.
How to check the furnace fan limit control switch wiring.
The fan limit switch temperature settings shown on the dial sketch are discussed separately.
Some furnaces will try a set number of times to start usually three if it fails then it will have to be reset with a power off before it works again.
Before testing the limit switch power off the furnace wait a few seconds and power it back on.
If there is a serviceman switch turn it off.
Locate the white limit switch.
If the gas solenoid is opening up but it is not sparking then the electrode would be suspect as the board sends a signal to the gas solenoid and electrode at the same time.
If the temperature of the combustion chamber exceeds the preset limit the switch will open and disrupt the flow of current to the circuit board in effect shutting down the main burner.
If the temperature inside of the plenum gets too hot it shuts off the gas supply to your burners to prevent your.
If not shut the power off at the breaker panel.
Once the plenum reaches a specific temperature the limit switch sends a signal to the air handler to begin running and delivering warm air to your home.
Ordered new limit switch atwood 37022 hydro flame limit switch 190 degrees around 15 with shipping paying attention to get one with correct limit temperature and also trying to find out with rv manufacturer for no reason i decided to contact them not atwood whether it s possible to take sail switch out without taking the furnace unit out.
A limit switch also acts as a safety device for your furnace.
How to check limit switches using your voltmeter.
Assure that the control has been installed and wired in accordance with the manufacturer s installation instructions using the following procedures.
To test a limit switch you ll want to check continuity to determine what state the switch is in.
It s function is to monitor the combustion chamber heat level.
It reads the temperature of the plenum and waits until it gets appropriately warm.
Remove the cover by lifting it upwards or pulling it off to reveal the body of the switch and two metal arms.
At fan limit control settings.
Depending on your furnace model the switch will be surrounded by a silver or white cover.