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.

 

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...