glow plug diagnosis question sdl - PeachParts Mercedes-Benz Forum

rosenfe · #1 08-23-2010, 12:23 PM

my glow plug light on dash is out,car will still start,but its still warm out,plugs were changed 2 years ago,in useing dieselgiant diagnosi,i checked fuse first by useing one lead on mu multimeter to battery positive terminal and one to either end of fuse checking dc voltage,no reading,in checking battery i do get the correct voltage,i havent checked power to relay at red wire yet,will do tonite,if no voltage reading at fuse-is this mean its bad.if no reading at red wire to relay is this mean relay could be bad.i tersted glow plugs at relay connector,one very high resistance others are at 1.0.

BoiseBenz · #2 08-23-2010, 12:45 PM

To test the glow fuse, you remove it and hold it in your hand. If it's one piece, it's good.

You also have one bad plug (high resistance) as you tested.

rosenfe · #3 08-23-2010, 12:56 PM

thanks,i have heard that fuse can have hailine crack not visible to eye,i will begin by changing out #3 plug with high resistance

Diesel911 · #4 08-23-2010, 05:46 PM

Quote:

Originally Posted by rosenfe

my glow plug light on dash is out,car will still start,but its still warm out,plugs were changed 2 years ago,in useing dieselgiant diagnosi,i checked fuse first by useing one lead on mu multimeter to battery positive terminal and one to either end of fuse checking dc voltage,no reading,in checking battery i do get the correct voltage,i havent checked power to relay at red wire yet,will do tonite,if no voltage reading at fuse-is this mean its bad.if no reading at red wire to relay is this mean relay could be bad.i tersted glow plugs at relay connector,one very high resistance others are at 1.0.

Relays do bo bad but it is more likely a Glow Plug.

The last time they were changed did you ream the Carbon out; or otherwise clean the Carbon out of the Glow Plug holes?

Also when you first turn the Key on does your Glow Plug Light go on with the rest of the warning lights like it is supposed to? If not they Bulb is burned out.

rosenfe · #5 08-23-2010, 06:26 PM

yes they were reamed out,would dash glow light come on even if there was a bad glow plug,

rosenfe · #6 08-23-2010, 06:27 PM

ill check tonite about bulb,i have to pull instrument cluster to get to it?

Diesel911 · #7 08-23-2010, 10:22 PM

Quote:

Originally Posted by rosenfe

yes they were reamed out,would dash glow light come on even if there was a bad glow plug,

When you first turn the Key all of the warning lights are supposed to light up and I believe that includes the Glow Plug Lamp (that is the test for a burnt out bulb).
My Wife is not home with the Car so I can not check that right now; I believe She has a class tinight.
Maybe someone else will speak up.

Yes, to change the bulb the Instrument Cluster needs to be pulled out.

Fattyman · #8 08-23-2010, 11:04 PM

The glow plug light will not come on if you have more than one plug that is NG. That and poor starting are the warning signs. If you have one bad plug change them all. Don't waste your time testing ohms, opens, continuity, etc.. By the time you go through all that it's easier just to put new ones on. You're done. Move on to the next challenge.