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How to check the health of relay J and M?
and can these be the culprit of delayed start as shown in the video?
Relay M is the real CRANKING relay for the starter solenoid.
Relay R is power to the transmission computer/module, where if the tranny computer is not ready or low voltage, the approval to CRANK the engine wont happen.
Relay N supplies many sensors on the engine, so if there is bad contact or loss of power to engine sensors, engine computer is also not ready to CRANK.
To test the relay you need 50 watts bulb, at least one, two is better as a LOAD. U can use ur car battery as power supply.
I can draw wiring diagram for you to test.
Simple test is warm up each suspect relay before you want to crank your engine.
This simple way you can weed out the "weak" relay. But this method does not help if relay contact points are worn out.
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The techy Sadel is a very good tech, he is a BMW familiar, but unfortunately not a Mercedes familiar.
Here familiarity with how W212 or Mercedes in general design/distribute/route their power Circuit 30 and Circuit 30g will be VERY important.
Someone with familiarity of W212 electrical system will track the root cause in under 10 minutes, as the pointers/clues are there on the first scan Sadel did in video minutes 3 ish.
So no need to tear down the steering column and whatever you see being removed.
The initial scanning has all the clues, I marked red.
This case also is very similar for its lots of communication errors as I explained post #3, simply because of very low voltage.
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The information that power feed Circuit 30 has issue......... is there on the scanner, see image Tranny 2 of 2, tranny module is the reporting module.
The information that power feed Circuit 30g has very low voltage is reported by Instrument Cluster module.
Its all there.
I have to repeat this again. LOW VOLTAGE will become more and more an issue with your W212, because it is aging now. Corrosion and oxidation and loose connections will be your enemy.
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So, for that 2014 MB video from DTech Engineering, all one need to do is see FRONT SAM and REAR SAM Voltages data , before touching or tearing down anything on the car.
Viola !!!! Under 10 minutes and by now you who is familiar with W212 Front SAM and F32 Prefuse box would have measured the output of F32 prefuse box for the said Circuit 30g and found out
that the fault lies there. That simple...YES.
So, if you want to DIY your W212, instead of The Playboy or Hustler Magazine to read during weekends or at night, go have fun with your car wiring diagrams.
PART 2 of Post #30. The 2014 MB No Power Steering and No Drive-Reverse.
If you have really watched the 2014 MB No Power Steering and No Drive-Reverse. video on post #30, you could be asking :
01. But the Electric Power Steering is not powered from 30g ?
Again , reminder : Loss Communication can also means module is DEAD or OFF or very low voltage.
The answer is : the F32 Prefuse box wiring diagram shows the direct feed for EPS from MR3 terminal, so when you inspect F32, you naturally will inspect MR3 connection too.
If you have read the post starting with post #1, which you should and then have downloaded my own "short-cut" documents using Excel format or MB OE documents on post #6, the answer is there :
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.EPS = Electric Power Steering. Sometimes at a glance I mis-read EPS as ESP Electronic Stability Program ....LOL
Issue is RESOLVED for now!
It was relay R
I tried interchanging relay R (Circuit 87) with relay O (Horn Relay) as they both look same and it worked. Till now no problem after interchanging! The relay is not short but has some malfunction which was causing the issue!
Now I have put it in the place of Horn relay. Horn is mostly working after interchanging but sometimes it is not.
Now I am worried about what caused the damage to that relay? And does relay gets damage partially without the fuse being blown.
Anyway, So nice of you sir!🙏🏻
Can’t thank you enough for your help, time and support!
Relay R some model has a recall read below of another member having the same issue:, but no CRANK delay, totally CAN NOT CRank, but his is gasoline engine
Here : https://mbworld.org/forums/e-class-w...ation-tcm.html
Check ur relay R types, at the REAR SAM also being used. I have replaced all 3 of mine because the numbers are under the recall.
Also relay R is a mini relay, so it wont be as robust as the bigger size relay like J,K L, P and M.
Relay is a wear and tear item. Its hinges the up/down movement, its contact points and sometime the coil insulation failed or weakened
When swapping relay, do not only find one of the same shape. It has to be the same pins assignment.
There's a legend at the relay side showing which is 86. 86, 30 and 87 or 87A pins. These MUST be the same.
I hope this thing hasn’t caused any sort of damage to any part of the car due to this defective relay.
As I have interchanged it with the horn relay. So shall I let it be this way or shall I get it replaced with new one as horn is working almost fine with this relay.
I hope this thing hasn’t caused any sort of damage to any part of the car due to this defective relay. <<<< NOPE, it wont. No Worry.
As I have interchanged it with the horn relay. So shall I let it be this way or shall I get it replaced with new one as horn is working almost fine with this relay.
Can I continue using these relays which I interchanged. Saying because the dealership is out of stoc of these relays and cannot place order as well.
You can still use them, no problem. Those Relays are not common and in Indonesia I need to special order them , waiting period 30+ days. You in India ?
I have spare relays, of all type and P/N as used on my car. I must have spare fuses and relays all the time. Also DO NOT buy cheap garbage fuse because their rating is bull**** and can burn your modules..
Buy branded fuses ONLY. USA or German made ones.
Do not use other than official genuine Mercedes Relays. Because they are good and using resistors to reduce voltage spike from the relay coils.
Voltage spike can kill computers/modules.
Read here : https://mbworld.org/forums/e-class-w...-not-know.html
01-18-2024, 10:50 AM
