Testing glow plugs

5K ohms across 12V is not going to do much heating, is it? (0.03 Watt!) Maybe you meant 5 Ohms? Though I would suggest 1 Ohm is closer to the mark.

Yep, on my Cruiser the resistance across a good glow plug is 0.7 Ohm. Can make it hard to see if they are good or not when using a cheap Ohm meter.

I stand corrected (I knew someone would - lol) It's been a few years since I had to check some on a Jeep Diesel and I couldn't remember the specifications. As HJ60-2H says it is hard to see the differences, but an open circuit glow plug is clear. Glow plugs can be sourced fairly cheaply (if you do some checking around). If they have been inservice for some time, it might pay to replace them all and keep the best ones for spares.

Garry