Hi there, My 87 300D suddenly decided to burn out the fuse strip in the glow plug relay. I don't have a wire diagram to see if I can find out why. I changed the glow plugs a little over a year ago, and it hasn't had a problem since then 'till last night. When I pillud the cover off of the relay, I could see traces of lots of heat, like it was a direct short, or it stuck in the on position, and overheated. Can anyone help me out with a diagram? Or does anyone have any ideas where I should start looking? Another question is what is the amp rating of that fuse strip, so I can replace it with a fusable link.

 

Thanks I have tested he glow plugs, all are good, the controller is on order it wasn't as expensive as I expected, I'm still going to look nto possibly repairing the old one, because they might not be so readilly available later on. I intend to keep and drive this car 'till repair isn't possible any more.

 

"...they might not be so readilly available later on. I intend to keep and drive this car 'till repair isn't possible any more."
I love your attitude! :-) I have an 87 300D Turbo with 256,000 miles on it and I too want to keep it as long as possible. (It most likely will outlive me as I am 84.) :-)
Last week I made a one-day round trip from Atlanta to Florida (Yalaha), all total about 800 miles. With the cruise control set at 80 mph I averaged 28 mpg. The car and the engine still run like new. :-)
About glow plugs: If I am not mistaken, the timer keeps them hot for about 20 seconds. By NOT cranking the engine for 5 seconds after the glow-plug light goes out, it will start almost immediately every time, even on cold days. :-)