glow plug lights - PeachParts Mercedes-Benz Forum

joro · #1 05-08-2007, 02:32 AM

My w124 300tdt glow plug light isnt coming on,car wil start normally actually even faster than other dieseld ive owned,but the yellow light isnt coming on.
fuse??
glow plugs??
any ideas,

help??

pjc · #2 05-08-2007, 08:02 AM

Could be just a burned out indicator bulb on your instrument cluster. If the engine is starting quickly, it sounds like the relay and plugs themselves are fine.

sokoloff · #3 05-08-2007, 08:34 AM

That light almost never burns out. I'd take an ohm meter and test the plugs. Good ones read about 0.6 ohms cold. Bad ones read infinite. A search will bring up all the details. In warm weather it might still start okay with a bad plug, but it sure ought to be addressed.

babymog · #4 05-08-2007, 08:53 AM

The light will not come on if #1 or two of the 5-6 are burned out.

sokoloff · #5 05-08-2007, 09:58 AM

I know on my 210 diesel that the glow plug and check engine light comes on when I have one bad glow plug. The 124 may not be wired the same way though.

joro · #6 05-08-2007, 12:15 PM

so it could very well be i have a bad glow plug then,i think ill change them all at once?
recommend??

Brian Carlton · #7 05-08-2007, 12:44 PM

Quote:

Originally Posted by joro

so it could very well be i have a bad glow plug then,i think ill change them all at once?
recommend??

You don't need to change them all if the engine has no starting problems. Just find the one or two bad plugs. They'll probably show infinite resistance when checked with an ohmmeter. Change them to Bosch or Beru.

You can buy them right on this site.........press the "buy parts" button at the top of the page. You'll be assured that they are correct for your vehicle and you support the forum.........which provides you with all the free advice that you could need.

joro · #8 05-08-2007, 04:50 PM

But how can i check them without removing them??

Brian Carlton · #9 05-08-2007, 05:01 PM

Quote:

Originally Posted by joro

But how can i check them without removing them??

Pull the plug at the glow plug relay. There are five sockets in the plug. Look carefully and you'll see the numbers on the face of the plug.

Connect one end of the ohmmeter to the socket and the other end to ground. You'll get about 1 ohm on the good plugs and the bad ones will likely be open.......or have resistances of 3 ohms or more.