Hello everyone,

I have a question/problem. I noticed today that when I went to start my car that when I turned on the ignition to let the glow plug light come on and then go off before starting my car, the glow plug light did not come on. In the owner's manual it says if the light does not come on the have it serviced. i checked the fuses and they all look ok. Does anyone have any suggestions. My MB service manual is on back order and I would like to get this fixed soon. It's not the light either b/c after three tries then the glow plug lamp will light up like it is suppose to then go out. Help. Thank you.

 

was the engine temp above 30 degrees celcius?

 

Yes, the engine temp was above 30 celsius which I believe is 86F. Yes it was when the engine was warm or hot both. I figured it could be the glow plug relay. Also I was looking and I do not see where these glow plugs have ever been replaced and MB recommends them to be replaced every two years. Thoughts or comments.

Thanks.

 

i only know that if the glow plug indicator lamp remain lit, that the glow plug is faulty.

pberku must know more about your case.

 

What does this mean?

 

Phil.

https://mercedesforum.com/showProfile.asp?memid=3554

 

The most likely causes, (in order) for the glow plug light not to come on are the following:

a) Two or more defective glow-plugs.

b) Either a burnt-out glow-plug 80-Amp strip fuse, a hair line crack in the fuse, or the fuse is not making proper contact at its screw terminals (Due to corrosion).

c) A defective Glow-plug relay.

d) Defective Glow-Plug Wires.

A typical symptom of defective glow-plugs is that the glow-plug light fails to light when the ignition is first tuned on but suddenly lights up after a few seconds, and remains lit for about 15-60 before turning off again. The engine is also harder to start, and idles rough, especially when cold.

Start by checking items "a", and "b" above. Glow-plug resistance should be less than 1 OHM each.


Phil

 

Ok so I need to check the resistance on the glow plugs? I am a newbie. I can use a little help. I need a voltmeter to check that correct? Once I get a voltmeter how exactly do I measure the resistance. I would imagine if the resistance is over 1 ohm then the glow pulg is bad. I checked all the fuses in the fuse panel last night and they all look good visually, is there anything I need to do here or should I just test the glow plugs. There did not appear to be any corrosion on the fuses.

Thank you for your help!

 

The glow-plug strip fuse is not located in the fuse box, but rather in the glow-plug relay box. The glow-plug relay box is a black box approximately 3W" x 3.5"L x 1"H, and sits on the driver's side fender, on the wheel well. Its easily visible.

Lift its black cover, and you will see the Glow-plug relay, the glow-plugs wire terminal, and the strip fuse. Check the strip fuse first, than unplug the glow-plug wire harness, and check the resistance between each glow-plug wire and a good ground. The resistance should be less than 1 OHM. ideally it should be less than 1/2 Ohm.

If you don't have an OHM meter than another way to check the glow plugs is as follows: With your glow-plug wire harness still unplugged at the glow-plug relay box, MOMENTARILY apply 12V directly to each glow-plug wire. If the glow-plug is OK you should get a hefty spark, If you get a weak spark, or no spark that glow-plug, or its associated wire is defective.

Again, make sure that your glow-plug wire terminal is UNPLUGGED . Be Careful not to short anything while applying the 12V, and make sure that you apply the 12 V to the wires that go directly to each glow-plugs, and not to any other wires. Do this with the ignition OFF. You can take the 12 V using a wire of at least 14 gauge. One end connected to your + of the Battery and the other end connected momentarily to each glow-plug wire as described.


Phil

 

Ok here is what I have found. I looked at the fuse, it was not broken. It did not have any corrosion on it either. Then I unplugged the glow plug wiring harness and tested each glow plug wire. I had my multimeter set on 200 Ohm as Haynes said to do. I connected it to a good ground and it said 1. I looked in the manual for the multimeter and it said to move to the next higher resistance so I did, 2000 Ohm, 1 also. Finally I switched it to 20K Ohm and it registered about 15 on all of the glow plug wires. Does this mean that they are all no good? Thanks for your help.

Dave