Quote:
Originally Posted by funola
I can't see how a glow plug can develop a short circuit. Open circuit, yes. Short? Very unlikely. I can see maybe if you left a wrench on the glow plug lead shorting it to ground, in which case the strip fuse will blow immediately. The problem with measuring glow plug resistance is that it is very difficult to measure it accurately due to lts low resistance, in the order of 1.2 to 1.5 ohms. Your run of the mill DVM will not do the job. High heat in the glow plug causes expansion/ contraction in the connections of the heater wire, which could give you erroneous readings in a flaky glow plug. Measuring current is the best way. Inductive ammeters don't 't lie. It works on the principle that a wire carrying a current through it will have a magnetic field around it proportional to the current. Try it, you will like it.
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I've had a plug that was short-circuited, so they do exist. The exact resistance that you measure isn't important. If you glow plug has a much higher resistance right after glowing than when it's cold, you know it works. End of story. There's no need to attach anything to your battery or add up any amperage.
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2004 VW Jetta TDI (manual)
Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL
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