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1983 240D
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Discussion Starter #1
Hi,

I posted an earlier post that got no replies. I was trying to diag my glow plug relay before dropping cash on a new one: http://www.benzworld.org/forums/w123-e-ce-d-cd-td-te-class/1376600-technical-diagnosing-glow-plug-relay.html#post2877476

I have 3 manuals: alldatadiy, cd's from mercedesmanuals.com, and the Haynes Diesel 123 manual.

None of them have the pinpoint test to tell me which voltages to expect on what pins.

Note I have a suspect short in the relay, no problems with the glow plugs. I have a short that drains about 250 Ma if the glow plugs are connected to the relay or not.

Where can I get comprehensive, step by step diagnostics to pinpoint electrical problems. Does anyone know where to find what I am asking for?
 

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1982 300TDT 150,000 miles 1985 380SE 130,000 miles 1991 560SEL 81,000 miles (a/k/a the nightmare)
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1983 240D
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27 Posts
Discussion Starter #3
Mercedes Diesel Glow Plug Repair

Now, you don't check everything through voltage testing... but the above should point you in the right direction.
Yes, I had already review those excellent instructions at dieselgiant.com. However, dieselgiants how to is covering the output side of the relay (blue in picture). I have a suspected short circuit on the control side of the relay (red in picture). My short circuit is the same amperage with the (blue) glow plug side connected or not.

I am not super experienced on this stuff, I could be completely wrong, but with the comprehensive pinpoint test instructions I know I can detect and isolate any problem without guessing. I have done it with my Lincoln. Does anyone know where those type of instructions for Mercedes can be found?
 

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if you end up droping some cash there is a bosch glow plug relay and four glow plugs, i think they describe it as a quick glow. 99.95. $100. best 100 i spent. i did buy it during the winter time though. so it was most needed. and youll need working glow plugs soon also. good luck.
 

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1983 240D
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Discussion Starter #5
if you end up droping some cash there is a bosch glow plug relay and four glow plugs, i think they describe it as a quick glow. 99.95. $100. best 100 i spent. i did buy it during the winter time though. so it was most needed. and youll need working glow plugs soon also. good luck.
my car starts right up. Glow plugs are working fine. I have a short somewhere and I suspect the glow plug relay ( see link above to my prior post). As a side note, my alt is recently rebuilt, and confirmed not the source of the short. Starter is recently rebuilt and confirmed not the source of the short. The short is related to circuit 2 (under the dash) and the glow plug relay.

I am just hoping that before I drop $ on a new relay that I can describe exactly what is out of spec on it. for example, what if the relay is fine but it is getting an input out of spec that makes it short? What if I am just completely wrong? After all, I am the first to admit I suck at fixing cars. Why I try is a topic for another thread.

I don't like to play the game of replacing electrical equipment based on guesses and hunches. That is why I am asking if anyone knows where I can get the step by step pinpoint diagnostics, or even factory specs for each circuit/pin.

thanks
 

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so i dont know if it means anything to you but this is what im reading out of my manual......"Do not short out the glow plugs to ground such as would happen if a screwdriver were placed between them and the engine block. this couls seriously damage the timer relay" maybe something like this happend, which i dont know why that would hurt it, but.....i guess it could. i hope this helps....even though im not really sure what your problem is.. dead battery i assume?
 

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1983 240D
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Discussion Starter #7
so i dont know if it means anything to you but this is what im reading out of my manual......"Do not short out the glow plugs to ground such as would happen if a screwdriver were placed between them and the engine block. this couls seriously damage the timer relay" maybe something like this happend, which i dont know why that would hurt it, but.....i guess it could. i hope this helps....even though im not really sure what your problem is.. dead battery i assume?
never took the glow plugs out. Car starts and charges fine. battery is fine. The problem is that I have a minor short somewhere, about 250 ma and it drains my battery if I don't disconnect it when parked.

As I explained above I have eliminated all other circuits and traced it to the best of my ability to the glow plug relay and/or something fed through the #2 fuse.

So I am asking if anyone can tell me where to get detailed electrical specs and troubleshooting instructions. I had a lincoln and the manual had a section called "pinpoint tests" where you could drill down to any electrical component based on voltages, conditions, amps, ohms, etc.

I already have haynes, alldata, and the mercedesmanuals CD's. None of these manuals have the specs and diagnostics I am looking for. Where can I find them?
 

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1983 240D
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Discussion Starter #8
one more try. . .

Does anybody know where to get the detailed electrical specs (pin level voltages, amperages, ohm ratings) and step by step diagnostics for w123?
 

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'82 300D
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Have you acutally unplugged the connection and thene tested for a short? Have you checked each and every port in the fuse box?

I have not seen detailed specs like that yet.

Have you tried posting on mecedesshop dot com?
 

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If you find them, please make sure to update us because apparently nobody around here has detailed diagnostic test instructions either. Might really help someone else in the future. But for now, it looks like you are the trailblazer on this one.
 

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1983 240D
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Discussion Starter #11
Have you acutally unplugged the connection and thene tested for a short? Have you checked each and every port in the fuse box?

I have not seen detailed specs like that yet.

Have you tried posting on mecedesshop dot com?
The evidence of suspected short is that I routed the ground through my ammeter and measured I can't remember now about 100-200 ma - most of the drain I measured at the negative battery terminal. The problem is that I don't know what the spec is - maybe this is normal. Maybe some other circuit on fuse #2 is shorted - causing an input to the relay and making it look like the short. I have seen that happen before and am not replacing a $200 relay until I know for sure.

Don't you hate it when you replace an electrical component and it doesn't fix the problem?
 

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The evidence of suspected short is that I routed the ground through my ammeter and measured I can't remember now about 100-200 ma - most of the drain I measured at the negative battery terminal. The problem is that I don't know what the spec is - maybe this is normal. Maybe some other circuit on fuse #2 is shorted - causing an input to the relay and making it look like the short. I have seen that happen before and am not replacing a $200 relay until I know for sure.

Don't you hate it when you replace an electrical component and it doesn't fix the problem?
Yes, I do hate it.

I wonder what the clock power draw is...also, when you tested for the short, were the doors or trunk open? Also, do you have an electronic radio w/memory?

Have you posted on mercedes shop yet? There is a user whunter, that has many years of MB certified mechanical experience.
 
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