Glow Plug Fuse Screw Tightness - Check It!

[Richard Howard]

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.

[sixto]

The main power cable to the glow relay and the strip fuse are live all the time. Make sure you don't touch a conductive item like a screwdriver to the car's body.

Sixto
87 300D

[1980sd]

May be a good idea to remove the battery cable before poking around in there.

Might as well check batt. connections while you're at it...

[Jeremy5848]

Electricians use a type of paste when joining copper and aluminum conductors to prevent an electrolytic reaction; the same stuff (in tiny amounts) can be used on the (aluminum) strip fuse to prevent it from corroding. Ditto the added-on strip fuse for the climate control blower in the W124 cars (and others?).

Jeremy