Again, colder weather is on the way for us north of the equator, prompting us to check our 4 and 5 cylinder diesels to be sure they're ready for low air temps.

When checking the glow plug system to be sure that no glowplugs are open-circuit and that each one shows the correct resistance to ground (remove the lead from the terminal before checking), be sure to check one other area that is sometimes overlooked.

Slide off the cover on the glow plug controller to expose the 80amp flat plate fuse and using an offset Phillips screwdriver, check the tightness of the two screws that hold the fuse in place.

If these screws are not tight the glow plugs can't draw enough current to produce the intended amount of heating, producing symptoms of glow plug failure and difficulty in starting from cold.

When I recently checked my '82 W126 300SD, I found both screws for the fuse not quite tight enough. Each needed about 1/5 turn more to tighten for low resistance current flow.

__________________
Respect, protect, and maintain complex systems - whether natural or of German design, to benefit from their full potential.

1982 300SD W126.120 with an OM617.950 from a W116.120
1984 300SD W126.120 with an OM617.951