This afternoon I was cleaning my car, for what ever reason I turned the key all the way to the right with out starting the engine. After a minute or two I started to smell something burning; the glow-plug fuse on the firewall was melting. The fuse it self stayed in tact but the screw started to melt out of the plastic holder. What is going on here, this is not the first time I switched the key all the way to the right with out starting the engine?

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).

To get heat from an electrical current, you have to have resistance. Normally there is not enough resistance in the glow plug circuit to cause enough heat to melt anything. However, if you have some corrosion on those connections, it can be a source of resistance that causes excessive heat.

You probably need to disconnect the high-current leads from the glow plug relay box and clean them thoroughly until they are shiny and can make a good electrical connection.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

With the glow plug relay box; you mean the one under the dash or the little box on the firewall?

I have to replace the one on the firewall and will look at all the conections and clean them. Do I use some fine sandpaper?

Thanks

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).