A veteran tech in Boise changed how I see glow plug testing

I was sure a bad glow plug would always show infinite resistance on a meter. Then, at a shop in Boise, a tech named Carl showed me one that read 0.6 ohms cold but would short internally once it got hot. He said, 'You can't trust the first check, you have to watch it under load.' Now I always do a running voltage drop test after a cold check. Has anyone else found a glow plug that tested okay cold but failed when warm?

3 comments

3 Comments

iris57416d ago

What's the best way to do a running voltage drop test?

pat_schmidt6016d ago

Wow, that's a solid tip right there. I read a forum post once where a guy kept having hard starts on a diesel, and his plugs all checked fine cold. He finally rigged up a test light to watch them while the controller cycled, and one would just drop out after a few seconds. Makes you wonder how many "good" plugs out there are actually bad when they get hot, doesn't it? That voltage drop test under load seems like the only real way to know for sure.

julia_miller2416d ago

Actually, a test light isn't the best tool for that job. It only shows if voltage is present, not how much is dropping. A digital multimeter gives you the real numbers you need for a proper voltage drop check.