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Old 11-14-2012, 09:13 AM
ytmtnman's Avatar
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What is the resistance limit for good glow plugs?

For an om617- what would the upper limit be? I have a few plugs that are testing at 4.5 to 6 ohms (engine warm, if that matters) and want to know if I should replace them.


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Old 11-14-2012, 09:45 AM
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1.5--2 ohms is what I've seen stated before. Yours seem high to me. Best way to check is to pull them out and put 12 volts to them.
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Old 11-14-2012, 11:12 AM
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Do NOT touch the glow plugs!!!!
Germantown, TN

Current Car --- 05/2012 1984 300D Light Ivory, Red interior
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Old 11-14-2012, 11:29 AM
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As the get hotter the element reistance of the glow plug increases. If you are getting say 1 ohm readings on some plugs and at the same time basically 4.5 ohms or so on others.

It is a pretty sure thing you have to examine things more carefully. Since there may be variables present. Pulling them and doing a direct voltage test application for observation may be best.

If a plug and its feed wire from the timer box is showing 4.5 ohms something is not normal.
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Old 11-14-2012, 02:04 PM
cho's Avatar
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you have to be precise
first do you meter correction readings
(probe wires head to head)

I practice to change any above 1 ohm - measured cold GP only.

from your post I would say that you have those 6 ohm to change


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