Standard HG Hot Water Pressure Washer Troubleshooting

What to do if the burner is not firing and how to check the MV terminal.

The first thing you should do if your hot water pressure washer burner is not firing is to make sure the unit has a pilot flame. If it does, you will then need to check if the ignition control box is seeing the flame correctly. To do this, you will need to locate and check the MV terminal on the hot water pressure washer. Every HEG unit has an ignition control box that is powered with a 24V AC the minute the pressure washer motor starts.

The ignition control box is mounted to the left of the water pump under a black metal cover. When a unit is started, the ignition control will create a spark and open the pilot solenoid on the gas valve to light the pilot flame. Once the ignition control box senses the pilot flame, it will send 24 volts of AC power out through the MV terminal. To check it properly, you will need to use a voltmeter. Place the black lead of the voltmeter on the TR ground terminal and the red lead of the voltmeter on the TH terminal.

So why is the MV terminal so important to check?

Without the 24 volts of AC power that is sent out through the MV terminal, no other part of the burner circuit on the hot water pressure washer will work. It’s the AC power that will power the main valve on the gas valve that’s used to light the burner ring. Regardless of what options are included, all HEG units have the same power circuit process. So, if there isn’t any power that is being sent out through the MV terminal, the sensing circuit on the machine will not be satisfied. You will need to make sure to check this terminal in the first steps of troubleshooting to narrow the variables down to the pilot flame, sensing rod and wire or the ignition control box itself. On isolated occasions, the grounding of the unit can affect the sensing circuits, so keep this in mind while working on these units. Typically, if your ignition control box is sending out 24 volts of AC power through the MV terminal, then the issue could simply be the replacement of a pressure switch or thermostat.

If your hot water pressure washer burner is still not firing after completing these steps, contact an authorized Mi-T-M Service Center or reach out to Mi-T-M Product Support at 800-553-9053.