I have an 300SDL 1986 benz and the glow plug light on the dash no longer lights up and the car is pretty hard to start. It just happened recently so i know it will be even harder to start once the colder weather sets in. Has anyone experienced this? Is it a relay switch and where can i find the part number to order the correct part and does anybody have a good place for ordering these parts? Thank you all in advance.

Tee.

 

With a multi-meter, you can test each of the six GP's, (0.1 to 0.9 on the ohms scale is good, a zero, or infinity means no good) and also check the relay for voltage to GP's. Also, look inside the relay box for the relay fuse, a 2" x 1/4" metal strip. They corrode and loose contact. Remove and replace, and, or, clean contacts anyway since they can appear good, but may not be!

 

In response to TEEPOLO.................

The glow plug relay should be located under the hood and atop the left (drivers side) inner wheel fender. Follow the wires connecting each GP into a wire harness and follow the wire harness that leads to a black plastic gp relay box atop inner fender. Lift the lid off the box and you can unplug the harness from the relay box and test each gp. Look for the fuse strip and remove and clean contacts, or if needed, replace the fuse strip.

My 87 300D has 253K on the clock.

 

Bob,
Thanks again for the quick response. I will check out the location you told me about and clean up the ends on the switch. Will and electric cleaner (like the spray) work? Should i also be looking for a part number specifically on this box? Thank you again. Have a great day.

 

This is a photo of the relay with the face cover off. See the 2 Philip's screws, they retain the strip fuse. Loosen screws and remove fuse. Clean (if needed) contacts, and fuse strip, with a small wire brush, or fine sand paper. You may use spark plug wire grease to coat the contacts to prevent future corrosion.

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