How to Troubleshoot a Mr. Heater Combustion Air Pressure Switch

Mr. Heater is a brand of portable space heaters commonly used in garages and workshops. Mr. Heater gas space heaters operate with a combustion air pressure switch that forces a measured quantity of air over a burner to oxygenate flame. If the heater's exhaust fan cuts on and shuts off repeatedly, the combustion air pressure switch may be malfunctioning. A simple test allows you to determine in a few minutes whether you must replace the switch.

Nut driver
Electrician's tape
Scissors or pocketknife

Instructions

- 1
  Shut off the heater at the main control and wait for the appliance to cool.
- 2
  Turn the corrugated knob on the gas tank or supply hose connected to the Mr. Heater clockwise to shut off the fuel supply.
- 3
  Remove the nuts securing the service plate of the Mr. Heater, using a nut driver. The service plate is on the back or the side of the Mr. Heater, depending on the model. The combustion air pressure switch is located near the back of the heater. A red wire and a brown wire connect to the switch.
- 4
  Grip the red and brown wires by the metal connector blades to pull them off the switch terminals.
- 5
  Hold the connector blades together and wrap them loosely with a piece of electrician's tape cut from the tape roll with scissors or a knife.
- 6
  Unscrew the knob on the gas tank or fuel line and light the Mr. Heater normally. If the heater ignites, the combustion air pressure switch is defective and must be replaced.

How to Adjust the Pressure Switch on a Goulds Pump

How to Replace a Door Switch on a Kenmore Microwave Oven

Appliance Repair