I measured the resistance of each glow plug by connecting the negative terminal of my voltmeter to battery ground, and then touching the positive terminal of the voltmeter to each of the female ends of the 5-prong plug on the glow plug relay.

My readings were all below one ohm, and I believe spec. for these is about 0.6 ohms.

I will perform one last test - measuring the voltage provided to each of the glow plugs with the glow plug harness disconnected. I should get about 12.5 volts there. If they ain't getting voltage, no current will flow......

At least the dealer had one in stock and was offering a good price on one - about $120 (I get 10% off for being an MBCA member) which is a better price than I found at a local europart place ($130) or on the internet from my usual supplier ($120). I was pleasantly surprised.

Chris