OK, I'm posting here just to make sure I've actually diagnosed my problem correctly. The glow plug pre-heater dashboard light went out last week and my starter would crank but the car wouldn't start. It's been sitting for days.

I finally got a multimeter and checked the battery: 12 volts, more or less

I opened the glow plug relay box, there was 12 volts at each side of the strip fuse.

I tested each hole of the relay connector that goes to the glow plugs, and each one read .9 or .8 ohms (and my multimeter seems to zero out at .3, so these readings were, I assume, a sign of good plugs).

But when I checked each of the 5 Pins in the relay box, with the ignition on, they read just a little more than 1 volt. Each one. While testing the last pin, I left the ignition on for a while, and something made a loud, squealing buzzing sound. If the relay were working right, the pins would have shown 12 volts, right?

In any event, do I assume that since the relay was getting 12V from the battery, and each glow plug was indicating proper resistance, and there was only 1 volt at each relay pin with the ignition on, that the relay isn't doing what it's supposed to, and that I should replace it?

Is replacing the relay as simple as it appears to be: unbolt it, attach the battery cable, and plug in the two connectors?

By the way, does anybody have any idea what might lead to a relay failure? I was having alternator issues right before this happened.

TIA
Michael

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1985 300TD Wagon
Running biodiesel whenever I can get it!