Video – How to Test Glow Plugs – The Supply Voltage & Timer Operation:

How to Measure the Glow Plug Resistance When Removed from the Vehicle.

How do You Test a Glow Plug Timer & the Supply Voltage?

It’s easy to check if you have a test meter (multimeter).

  • Remove one of the glow plug connections and connect your test meter.
  • Switch on the ignition (but don’t start your engine).
  • Check how long the timer (control module, or relay) voltage is supplied to each of the glow plugs. It should be for around 10 to 20 seconds dependant on the vehicle.
  • Whilst checking the timer, you can also check the supply voltage is correct.


You will have to switch the ignition off and on, each time you check a glow plug – To reset the supply voltage timer.

Other Glow Plug Videos:

How to Test Glow Plugs:

More Detailed Info:

More detailed information can be found on this page: Diesel Won’t Start When Cold – How to Fix Glow Plugs: (Opens in a new window / tab)