Glow plug diagnostics

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Glow plug diagnostics

Post by iPupGary »

A large percentage of glow plug bus bars and glow plugs I’ve seen under the hood are in dire need of a cleanup. If you are experiencing intermittent problems then you have more of a reason to clean up your connections. At these high currents it doesn't take much of a bad connection to cause problems. Use a dremel tool with a suitable abrasive tool or a wire wheel to clean both sides of the bus bar and the glow plug terminals.

I measured the glow plug circuit voltage and current for my truck. The voltage at the bus bar to ground, for the rapid heating circuit (relay #1), varies from 4.08 to 7.16 VDC over a 6.5 second period. The normal heating circuit (relay # 2) held steady at 4.4 VDC. See the attached graphs. The glow plug resistance is non-linear at higher currents (relay #1) and linear at lower currents (relay #2).

If you connect a stock glow plug to 12 VDC, it should heat in less than a second. Don’t heat it any longer than one second or you may fry your glow plug.

Last edited by JoeIsuzu on Sat Jul 02, 2011 12:27 pm, edited 1 time in total.
Reason: This was good enough that I pulled it out of another topic. Thanks, Gary!
1982 Chevy Luv 2wd short bed diesel w/ veggie conversion (under construction)
1999 Isuzu Trooper 3.5L Gas
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