I had a weird thing happen on my '83 240D that I am restoring to road-worthiness.

I had been able to start the car with no problems (I was debugging the door locks) and all was well. However, once, when I went to start it (after having started it 30 minutes prior), it would barely turn over. A charger placed on the battery showed a huge current draw on the charger meter.

I wanted to get a new battery anyway, so I got a nice new 1000CCA AGM battery and when I connected the plus terminal, I noticed an arc- like the headlights were on or something (they were not). I didn't leave it hooked up.

After messing with it today, it is acting normal.

Anyway, I think that maybe the glow plug relay was staying on. How common is this? It is the original relay, and the car sat unused in a barn for 15 years. I've been messing with this car for 9 months and not seen the relay fail. Can I take the relay apart and clean/lube?

Apply a volt meter to your battery and see what the voltage is. If it is under the voltage of a fully charged battery disconnect the electrical connectors at the glow plug relay.

After that if the voltage goes up that is a good indication that the relay was still on.

However there is another test. On the Glow Plug Relay is a flat copper Wire that is always connected to the Battery Voltage. Remove the screw and bend the wire away from the terminal and that cuts off all of the voltage to the relay with the exception of the Ignition Switch Voltage when it is in pre-glow.

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84 300D, 82 Volvo 244Gl Diesel

I wasn't clear in my description. My question really is how common is it for the glow plug relay to stick on?

Whatever the problem was, it is intermittent and is gone now. I can hang a voltmeter on one of the glows and see if it getting power or not (and it is not now except during pre-glow).

If I see this happen again, I'll just wire up a relay for manual control of glow plugs.

Thanks

It is not very frequent for the relay to stick but ususally when it happens it stays stuck. When it happens people who took the relay apart said they found the contacts of one of the relays welded together.

Adding this: When you are cranking the starter the glow are on by way of a wire in your case that goes to the Starter Solenoid.
On mine that goes to a Termnal Block on the Fender but only the turboed models have it and also in my case that wire is Purple/Violet.

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84 300D, 82 Volvo 244Gl Diesel