W115 salt shaker too hot too fast

[Cdowns]

Hey all I have a 73 220d. This is my first post here. I have done a bit of searching on this topic but no cases arise quite like mine. And have checked over many forum and search platforms. (Too many names for this indicator made it hard to search..)

I recently had to replace the entire glow plug control or salt shaker as some call it due to a broken filament. It would randomly get too hot too fast and for cold starts or even a warm start- and when it didn't heat up fast earlier.. Very random.

I replaced it- but the filament gets too hot too fast. This is as if I have been holding the plugs to get warmer for a few minutes- but happens almost instantly- which will cause my filament to break again. (And cannot start the car for fear of this)

I searched online and the engine bay for the location of the glow plug relay- could not find it- nor could I find it in my w115 manual- also I have read there is no fuse on my car for it? That didn't sound right though?

The only thing that I think it could possibly be is a bad ground somewhere or the fuse has somehow fused?- wanted to ask here first incase it is an easier fix than chasing wires.. And replacing different parts of the system..


Please let me know on thoughts!

- Chris

[Skippy]

If I'm correctly recalling the way your system is meant to work, the glow plugs are in series, and the salt shaker is also in series, acting sort of like a fifth plug. What it sounds like is someone rewired the system improperly, putting the salt shaker in parallel with one or more of the plugs. Check your glow plug wiring and see if this is the case. If visual inspection leaves any doubt, use an ohm meter to check resistance between two points before and after a given component.

[Diesel911]

I don't believe the Cars that have the "Salt Shaker" have a Glow Plug Relay and there is no Fuse showing in the Wiring Diagram.

You need to see if you really have the old loop/filiment type Glow Plugs and not the updated adapter Pencile type.

If you have the old loop/filiment type Glow Plutg the Zig-zag grid wires should not be touching the Block or any place where it would ground.
And, the way the Glow Plugs are wired needs to be inspected.

[Diesel911]

If Carbon build up around area 13; the red circles I believe Electricity will get conducted through the Carbon grounding the Glow Plug to the Head. This type of Glow Plug is not grounded to the Head like a Spark Plug or the later type Pencil Glow Plugs are..

[Shortsguy1]

I think the above replies are dead on correct. You must have a bad connection or electrical short somewhere. Normally, the battery's 12V divides across each glow plug (and shaker indicator), but you must have more than 12/5 V sometimes getting applied to your indicator wire. Good luck.

[Cdowns]

Hey, thanks for the detailed replies! Very helpful, I will read up how to clean the plugs as I am pretty positive I have the original plugs in there. I intend on doing the upgrade to the pencil plugs.

Thanks again for the replies, that all makes sense.


- Chris

[Diesel911]

I forgot to mention that I believe item 5 in the Wiring Diagram is the Glow Plug Resistor Controller is the Salt Shaker.
The other items labled as Resistors are the Zig-zag Wires.

Don't test the original Glow Plugs acrossed the Battery as you will quickly burn the Filiment that is not made to take the full 12 Volts.

[Cdowns]

Hey guys, I took the plugs out and cleaned them. I also tried to get rid of the extra Carbon build up inside the block as well.

I checked before I took everything apart if there was any ground issues with the zig zag type pieces and nothing was touching. - The same issue still arose.

I feel there my be a bigger problem And need to get a volt meter/ ohm tester to test - I am going to take everything apart again and inspect a bit more thoroughly - also start to trace wires a bit more and see if I can find something wrong in the system.

Wish me luck!

- Chris

[Diesel911]

Best Wishes

[robertchmar]

Hello Chris

I have the same problem with my w115 220d. Have you solve the problem on your car?

Thanks

[barry12345]

Sounds like the two of you may need to seek out an electrical friendly guy.

You both should also own a not expensive digital meter. Without one things like this can become difficult. Do not take a simple problem like this to a mechanic. Either a friend or dad can perhaps help. A great learning opportunity.

Both of you are perhaps young and it is an ever increasing electrical world. So even a limited amount of electrical knowledge can save you a fortune over the years.

The salt shaker being too bright indicates it is getting too much voltage across it somehow. If you know what a series string is something is shorted along that string that should not be. Basically the resistance in the circuit has been lowered with a defect present.


A test with no meter. The very front glow plug should have a wire going to ground. Disconnect that wire. If the salt shaker still lights after you have a short. A short is basically a point that the electrical energy is being directed to ground. Where by design it was not intended. If there is no wire going to ground at that front glow plug you have the universal parallel replacement plugs in the engine.

If this is so do nothing else but post that information first. This you can manage. As you mention no sense in burning out the indicator glow plug.

Also all people should know ohms law. It is not really hard to learn. It can help give insight into electrical things. Books explaining ohms law and how you apply it are still very common. To my way of thinking it is the basic foundation of understanding electrical things.

Without that pretty easily understood knowledge electrical issues can be hard. Again a friend or dad can help a person understand it if they find it hard to grasp. Actually one might find it interesting as well.

I am a hopefully still a younger thinking 75 year old guy. Stlll very interested in many things. Currently. I would like to be working on some of my cars as doing so is a mentally relaxing experience for me. Instead I am doing a fair amount of work in upgrading our house that we built 45 years ago. Renovation in some ways is harder than the original build. Keeps the wife happy as well. That tends to be job number one if you want a good life has also been my experience over the many years.

[robertchmar]

Hello

Great post barry12345.
In cold start the light (resistance) don't appear.
Well! Let's do something about this great w115, and good lock with your upgrading house, it's also nice.

Best regards

[robertchmar]

Barry12345

I have amuse myself reading a cdi of a motorcycle by mesure ohms between conectors - but i'm not yet a professional.

In my car there is no wire going to ground at that front glow plug! So I have an universal parallel replacement plugs in the engine?

Thanks

[barry12345]

Not there to examine things personally. So next question.

Do you have some squigily bent bare wires between the glow plugs present or not? Or do you have one normal looking wire from glow plug to glow plug. If it basically is one wire with insulation on it. Plus there is no ground by wire at the front glow plug. Then you have the 12 volt replacement upgrade glow plugs.

If this is true then the indicator glow plug will indeed burn out unless it is replaced also with a 12 volt conversion type. If it has not been already.

I again never having owned one of these cars assume. Assumptions of course can be inaccurate and dangerous. That the manufacturer put a glow plug in the salt shaker as a glow circuit on indicator. Someone that knows correct me if wrong.

Another small amount of help would be appreciated by any member. This poster had the glow plugs out. The original low voltage type had a loop on the end for an element. I have never had one of the 12 volt conversion glow plugs in my hands. Do they also have a loop or are they more like the pencil style of element end?

This thread is probably going to involve several back and forth exchanges before things are sorted out. No ground wire from the first glow plug at the front of the engine at a minumin suggests there probably are the conversion plugs present. Just trying to establish certain things before going on.

[robertchmar]

Hello Barry12345

The sistem is in serie like You did say... it ends in the front of motor... (Mercedes-Benz 220d 1971)

I dismounted almost everything ... beginner error ... like the plugs have been changed recently i haven't check them.

And then surprise of surprise:

I have mesure the continuety in the first one, nothing... take the first one out, and what I find... the first one was burn/cut ... like the circuit is in serie and cut in the first plug, of corse that no jus will pass to the indicator plug... the circuit was cut

the indicator plug have shine too much maybe because of the inicial burn of the first plug, and after don't shine at all because the circuit was cut...

let's now cross fingrers to not have excess of voltage in the circuit!!!

I start to become depressive with to much wires and possibilities... now it's everything ok... well! for now.

Big lesson for now: don't trust in new plugs they can burn any way!!!

big chance that a part of the plug didn't fall in the combustion chamber!!! Uff!
big chance also that i have turn to off the key in the right time to avoid burning the indicator glow plug!!! Uff!

I have reassemble almost everything, and let's test it... so far so good

It's running/starting again normaly... let's check the oil and put some diesel and let's «fly» tomorrow...

Many thanks Barry12345, if You have any problem/doubt with your «upgrade House» tell me... i can help you... since i will not help You with electrical issue in your cars.

Many thanks to All.


Best regards
Robert