Vauxhall Astra G Estate 1.7dti Diagnostics – Glow Plug Resistence

SoI have a glow plug fault and to try and narrow it down I thought I would check the resistance of them.

Parts required: Multimeter that has Ohm function

1, Identify glow plug location

2, The connectors have a serated type plastic on either sides, if you push these in and pull up the connector will come off the glow plug. Note the 2 underneath the ECU can be a bit fidly especially if you don’t have lanky fingers like me 😉

3, Switch on your multi-meter and select the Ohm function. Now to need to find our baseline resistance value. For this touch the positive and negative ends together and you should now get a reading on the screen mine was 0.7 (this value will vary on device quality/calibration etc so don’t worry if it’s not the same as mine).

5, Attach the black probe to the negative post of your battery.

6, With the red probe touch the tip of the first glow plug and your multi-meter should display a value. Mine was 1.3

Now the working value range seems to vary greatly depending on which website you read. A few say it should be between 0.1 and 6 ohm but after some reading I concluded that if it’s either zero or stupidly high then it’s likely to be dead. In order to get the resistance value you need to subtract the value gained in step 3 (mine was 0.7) from the value you have just got from step 6 i.e 1.3 so 1.3-0.7=0.6

8, Do the above for each glow plug until you’ve done all four.

Result: Four plug one I got 1.4 plug two 1.3 so all good BUT when I got to plug 3 I got 73.4 which is obviously well out of range, I tested it a few times just to be sure. Plug 4 was 1.4

So it appears my third plug is dead so will be ordering a replacement set.

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