1.Check the Pressure Switch connections at the Main board and at the switch.

2.Unplug the unit. Take a resistance reading from the Main board. Pin 1 to Pin 3 should read 20 to 25 ohms. If the resistance is okay, proceed to the next step. If an open is read, disconnect the harness from the pressure sensor and check resistance again. If the resistance is okay, suspect a harness issue. If the resistance still reads open, replace the pressure sensor.

3.Plug in the unit and power on. With the pressure sensor connected, measure voltage from Pin 2 to Pin 3 and Pin 2 to Pin 1. Both should read 2.5-3Vdc.

4.Inspect the pressure sensor hose for a blockage, or small pin hole in the pressure tubing allowing air to escape giving erratic reading or no pressure reading.

See your individual diagram to help identify the colors of wires for the model you are working on.