In Situ Glow Plug Tester with no vehicle battery help needed

Thread Starter

Mr Blue Sky

Joined Sep 16, 2013
Im working on an idea for testing glow plugs on engines that are not fitted to vehicles, and hence have no power supply.

The plan I have invloves using a 9v pp3 battery to power the circuit, as I dont think there will be much drain.

I will explain a little furthur..

There are 4 glow plugs fitted, each of around 1ohm (plus or minus .2 ohm), what I need to do is design a tool that will attach quickly to the glow plug head and check the resistance.

If the resistance is correct, to display a green led. If the resistance is over 1.2 ohm to display a red led and if the circuit is open to either display a red led or both the green and red leds.

I´ve sorted how to display with an open circuit either using a npn or pnp transistor, and think Ive found a way of returning a value when testing for resistance with a closed circuit, but I´m having trouble joining them together.

Ill try and upload my wiring diagrams shortly.

Thank you for your time and feedback.


Joined Aug 30, 2007
You'll need more current than a 9v battery can supply, they typically draw several amps each.
Here's a couple of videos showing testing methods...