How do I adjust my fan limit control?

Check with your owner’s manual for suggested temperatures. For a general guide, set the two lowest ones (from the furthest left) to 100 and 130 degrees to control when the fan comes on and goes off. The third marker should be set around 200 degrees as a safety shut-off for the burner.

What is a fan limit control?

A control which turns the blower fan on or off depending on the air temperature within the furnace. A high limit setting, which turns off the heat source or burner if the furnace overheats to dangerous temperatures. A blower fan Manual ON switch is also included on many fan limit controls.

How do I know if my fan limit switch is bad?

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 fan limit control switch located?

The fan limit switch sits on a mounting plate and has a long temperature sensor that extends into the furnace plenum: an air chamber that fills with air from the blower fan. The plate has a wire that runs to the blower and one that goes to the gas valve.

How to troubleshoot the fan limit control switch?

Troubleshooting the Fan Limit Control Switch on a Furnace, Temperature Settings, How it Works! – YouTube If playback doesn’t begin shortly, try restarting your device.

How to check a Honeywell Furnace Fan limit switch?

Honeywell provides a very simple fan limit switch checkout procedure to be used after the switch is installed: Disconnect the fan motor circuit at the L4064. Turn on power and set thermostat to call for heat. Burner should come on and limit controller should shut burner off when plenum temperature reaches the limit set point.

Where is the fan limit control on a gas furnace?

The fan limit control includes a sensor (not visible in the photographs) that projects into the supply air plenum – on gas furnaces this is typically an area above the furnace heat exchanger.

What kind of fan control switch does Zettler use?

Cam-stat® type Fan Limit Control Switch such as the A-1 Components BC 7070 Blower Controller, shown above. This limit control, model BC-7070-A/M is produced by Zettler or A-1 Components.