where are the glowplug relays? - PeachParts Mercedes-Benz Forum

TurboSDL · #1 08-26-2007, 01:19 AM

i dont know where the relays to the glowplugs or the fuses for them are located, i have an 87 300sdl, can anyone tell me or show me a pic? it would be greatly appreciated. thanks

Jeremy5848 · #2 08-26-2007, 01:40 AM

Your SDL is a different model than my 87 300D but....

The glow plug relay is on the left (driver's side) inner fender, near the brake booster. Your may be in a different place but will be similar in appearance.

Photo credit: not mine. Shamelessly stolen from another thread.

Jeremy

#3 08-26-2007, 01:48 AM

The fuse (Only 1) is under the lid of the glowplug relay.

TurboSDL · #4 08-26-2007, 05:00 AM

thanks ill check it in the morning and get back to you.

TurboSDL · #5 08-26-2007, 11:18 AM

ok i took the cap off of the relay and the strip fuse that uses 2 phillips is fried, i tried to jump the fuse using a real thick paper clip and it got real hot and orange, do u have any idea y this could be happening?

#6 08-26-2007, 11:22 AM

Did the paper clip heat up with the key off, or was it in the glow position?

TurboSDL · #7 08-26-2007, 11:55 AM

it heated up in the glow position, it was one of those real thick paperclips too, it heated up til it started to smoke and the clip just ended up breaking, could a bad glowplug cause this? obviously i found the source of the problem i just dont kno where to start looking for problems.

Jeremy5848 · #8 08-26-2007, 12:13 PM

The fuse (technically it's a "fusible link") is rated at 80 Amps so a big paperclip might not be enough. Nevertheless, fuses don't just fry because they're bored, but because something is drawing too much current.

If you have enough big paper clips, try this test. Disconnect all glowplug wires but one. Install paper clip in fuse position, turn key to preglow position. If OK, disconnect that glowplug wire and try another. Continue until you find one that makes the paperclip glow and smoke. That glowplug is shorted. Replace it.

The relay itself might also be shorted but I'd test the glowplugs themselves first.

Jeremy

TurboSDL · #9 08-26-2007, 12:35 PM

i noticed the number one, or the closest plug to the front of the car; the wire was a little stripped by the connection to the glowplug itself and it was touching the intake manifold, could this cause the problem? im looking for a new paper clip to test it.

Sbean · #10 08-26-2007, 02:34 PM

It sounds like you've found the problem. A short circuit to ground (manifold) is exactly the kind of thing that will cause the fuse to burn out. That's better than letting it cook until it starts a fire. Steve

pjc · #11 08-26-2007, 02:39 PM

If the metal wire is touching the manifold, you have a short (improper ground), and that's most likely what caused the fusible link to blow. Wrap that wire in something to insulate it (preferably electrical tape) and then you can try Jeremy5848's test above.

From other posts, I understand the fusible link is cheap to replace. That should be your next step before dropping $100+ on a new relay.

But if the insulation has gone bad at one spot on your GP harness, you need to inspect the whole thing for other trouble spots, and for continuity.

A word of caution: You can use a typical multimeter to test GP resistance, cable continuity, and in/out voltage, but not current draw. Most multimeters can't handle more than a couple of amps, and these GPs can draw a lot more than that.