To perform this method of testing, you will need a reliable 12v power source. You could use a spare 12v battery and jumper cables. In this case, a battery "jumper" box was used.

If you are testing a glow plug that is new from the box, you can begin here.

If you are testing a plug that is currently in your engine to see if it is the bad plug, you will need to first remove it; see the glow plug replacement guide for advice on this process.

Start the test by gripping the body of the glow plug with the negative cable clamp.