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Inspecting & Cleaning Ground Points + Improving Them
Hi Gang,
I only done the engine bay side and all ground points supporting that area.
This is because them points has the worst working condition by heat and by dirt.
W70 and W9 ground points
Location of W2/1 ground point for my car is at the LEFT side near and underneath W70 and W9. Not on the car right side as per WIS.
For my car, W2/1 is the electric power steering. I have not looked up and verify this via schematic, I trace it physically.
W2 ground point
There is a ground point to transmission + engine bell housing interface, which means this is closest to starter motor, but I can't find its ID number from WIS.
Also it is not indicated in where we can see starter motor in a schematic, example Start Stop System.
This is the biggest cable of all, same size as the negative battery cable to front strut top mount , the W10 ground point.
Left side CAT is the reference location for my car.
I can't access the cable end at bell housing, so that one I can't clean . Only can clean the other end.
W11 or ECM/ECU wiring assy ground. Opening up those clips at this plastic cable duct is a nightmare. I don't want to break anything, so gentle I must be.
2 final clip facing firewall, that I can't open due to no room for me to "dig" out the clip. Must create a special tool for jacking up this clips nicely and non-breaking.
thank you for digging in grounds 🙂 They are the important return half of the electrical circuit. (Same as the Neutral leg in building 120/220VAC!) chess Kingpin
Starting with the main battery brass grounding point shown above: it is open on top and acts as an unfortunate water funnel...
electric magic
I found mine was visibly corroded green already so I brushed it and added electric grease - See pic: used for all aluminum splices from hardware store to prevent oxidation.
The best thing would be to find a cap for that giant brass nut -or fill the top with epoxy... but here in California we are under a rain drought ! 🙂
MOST IMPORTANT GND...:
-- Battery - Chassis -- Body - Engine
SOURCE OF GND CORROSION :
-- high currents
-- salty road spray
-- disimilar metals
-- ALL of the above combo!🙂
Our average Ohmmeter is really not precise for fractions of Ohm. A reading of "0.2" is from the two test leads themselves. The actual tiny measure is hardly significant.
It's best to prefer test underload using the "min/max" DVM Setting to capture peak drop-voltage.
PRACTICALLY: Under the 350Amp starter load, it only takes a 0.014 ohm resistor to drop 5V... boom now practically powered by 7.6V !!!
All the fundamentals are always relevant: GND's are never to be forgotten. A rusty ground strap helps kill an aged starter by jacking up peak currents
P = U x I
Take 10mn to inspect you main GND points around 60kMi
✌️
Last edited by CaliBenzDriver; 05-29-2021 at 08:46 PM.
Reason: pics
I am not a fan of di-eletric grease. I dont know why.
Applied wrong they are actually resistance maker, hence the name di-electric.
Let's carry on............
W10 grounding point. Battery negative cable to front strut area.
What I like about MB for its grounds are :
01. It uses welded stud, instead of female thread at body and with a bolt ...as found on other cars.
02. It uses not only mechanical crimping at cable ends, but also soldering.
Ground Cable size wise, it is decent.
Here are my own improvements. This is stage 1, I will improve it better next time when can access the alternator in full.
Insurance. If and when the big cable to engine/transmission bell housing come loose or heavy oxidation. Below is the back-up.
35mm ( mm square ) welding wire. Superflex ( Australia ) , rated for continuos duty temperature 90C. Double insulated. Albeit this is a ground wire, I only want a robust one. https://www.weldconnect.com.au/cigwe...lex-weld-cable
I use green color 3M electrical tape to tone down the so obvious orange color and green is "ground/earth" color in IEC and also USA NEC.
It is the orange one. The copper strands are so fine and plenty and that made the cable so flexible despite double fat insulation, it is so nice to route this cable.
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Next time for Stage 2, I will do a better nickle plated copper bus bar and will use both 2 bolts of the alternator as securing/mounting points and hence also a wider contact surface area.
I choose the alternator because it is easiest to work on with big cables and alternator is also a power source.
From the alternator it also goes to grounding point W2.
The small black cable piggy back to the orange cable is a 16mm NYAF( corrected 31May 2021) cable. This cable set was the one I used for alternator output reading . So basically that is a 51 mm2 (corrected 31 May 2021) cable/s.
The 2 big cable to the alternator are secured down as such 3-4cm of play is possible between alternator to front subframe and subframe to engine bay.
3cm is to factor in the movement/play of engine mounts.
Again, from the alternator, I use a 6mm cable running towards cylinder head left and right.
This black cable BetaFlam Solar 125 can handle 120C operating temperature . It is solar panel application wire. Extremely high spec. This cable will experience the highest heat, compared to the orange one. https://publications.leoni.com/filea...pdf?1477313240
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Some of you may wonder, why the heck would I need to run the 6mm wire for both side cylinder heads ?
Well, you can't beat copper for one of the lowest resistance metal.
I also don't like the fact that cylider heads has gasket and needing to rely again on female thread and bolts for electron path...nahh, as direct & clean as possible is best.
What more would I improve ?
I would like a 2nd or bigger cable for negative wire to battery's sensor if possible
I will update when I am done testing.
This ground improvement is the least I can do for higher durability and hopefully it can assist reduced voltage loss at ECM when the dumb-azz ECO charging decided to suck down the battery.
11.8V at ECM is a sad affair you know....
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Last edited by S-Prihadi; 05-30-2021 at 04:22 PM.
Reason: Data correction - 31 May 2021
I could not agree more with you about dielectric silicon. It's mostly good to ocupy air space to prevent high-voltage ionisation arcs (30kV spark plugs).
I use a specialty grease that apears to be loaded with graphite carbon. It keeps contact oxidation minimal such as an air-tight wrap. Wherever it is you're guaranteed to gave no salt water and no available oxygen contact 👍
it's a good antioxidant but only for low temperature application. It's for building electrical.
There must be equivalent product with automotive grade to withstand engine heat.
Do you think the Loctite (red/blue) is detrimental to good ground contacts -or can it help keep contaminants out??
(I kind of think of blue Loctite as beneficial...)
Loctite blue or red, the thread locker ones will surely impede good electrical contact.
So far for high power connection, clean and firm/torqued well connectors with sufficient surface area as in bus bar or the cable lug itself is what has worked well for me.
I did a short run 30th May 2021 morning to test the improved grounding and at the same time setting the baseline thermal value for the air-cond pipes insulation project.
So far I am quite happy, I am like 0.25 Volt better now at ECM lowest voltage when the ECo algo decided to discharge the battery long enough.
I have not seen lower than 12.1V for longer than 0.5 second, compared up to as low as 11.8V previously.
Also it is true that air-cond blower at MAX speed will produce 14.3V constant with charging between 20 - 8 amps fluctuating. Basically its higher than absorption phase we normally see in a smart charging.
None, the cleaning and inspection is a routine thing I will conduct as preventive.
It is now a 7 years old car of 2014, so must inspect here and there and at the same time I wanted to see ECM/ECU grounding, how it is done.
Electrical contact cleanliness and torque down value on bolts/nuts for electrical connection is something we have to pay attention , also because they are the easiest to do.
When the car aged more, all push-in connectors must be inspected and cleaned. This is a bit on the tough side to define its contact firmness or total cleanliness.
At the least visual check for any oxidation will do good.
I focus those in unfriendly areas like engine bay or under-carriage, not those cool and clean ones inside the cabin.
The improvement side with extra cable is a different thing. I have explained why I did them.
D5 is an aerosol with 95% carrier, 5% actual deoxit. D100 is a liquid, sold in a small dropper bottle, of 100% deoxit, which has a consistency similar to Triflow or other such light oil lubricants. I've restored many a vintage mercedes switch with this stuff, especially the seat and window switches for a W124.
I have had very good results cleaning oxidized electrical contact surfaces using a clean soft pink pencil eraser, and a bit of D100. this works especially well on gold plated edge connectors such as are used on computer boards. if its particularlly oxidized, i'll start with a dry eraser, then finish with a bit of the d100.
re: amazon, ah once again I neglected to look where you are.
Before grounding system improvement. Control Module Voltage aka N3/10 akan ECU/ECM
After
14th May was high RPM to clean carbon and that may also get ECO algo to discharge more often, thinking I am accelerating hard.
1st June was not so much high RPM. But overall 0.25V improvement is by average I am getting at longest drain.
The video below can't be made to sync apple to apple for drain/discharge duration, but it helps to see it in real time whats happening.
Next I am going to mess with Front SAM N10/1. Now I am messing with F32 PreFuse.
Waiting for special Torx T15 tool I am modifying, so that I do not need to remove wiper's plastic water tray/vent/seal thingy which is blocking . The L type Torx I have can't reach in....damn.
On the front SAM N10/1 , probably I will not tear it open 100% separating the power PCB from the computer/electronic PCB.
I need to verify this :
From F32 to N10-1 Front SAM to N3-10 ECM .
Take a closer look above. 6mm size wire from F32 terminal MR6, supposedly dedicated to feed only a 7.5A fuse ( stationed at Front SAM N10/1 ) for ECM or N3/10 ( 0.75mm wire ) and Ignition Module N73 (0.5mm wire ).
The voltage drop should never be as bad as what I am getting at ECM, as reported by the ECM itself via OBD2. If 7.5A fuse is used, consumption itself should be at 5-6 amps at best.
Improving the grounding to both side of the cylinder heads has showed decent improvement.
So we know the negative feed path was not that good, because it has to go thru :
Battery Negative Post W10 >>>car metal frame >> unamed ground point from car under-carriage to engine block near starter>>>>engine block>>>bolts & gasket>>>cylinder head>>>ECM grounding called W11.
My negative path to ECM grounding W11 is more drect and all copper based, no aluminum or steel :
Battery Negative Post W10>>35mm copper cable approx 3.5 meters to custom alternator's copper bus bar>>6mm copper cable of approx 2.5 meters direct to cable lug of W11 ECM ground.
Now look at integrity of connections.
At F32, terminal MR6 feeding the 6mm cable for the 7.5A fuse at N10/1 Front SAM is solid, nut based. Clean and tight. Ignore the fact that WIS F32 document indicated red main color for all of these wires
Looking at used front SAM N10/1 photos, the connectors used is most likely a push type, friction fit type.
The reason I want to inspect the Front SAM N10/1 is to make sure the 6mm cable into it ( for the ECM ) is all good clean and tight.
Later I will get this type of fuse jumper
I will then able to measure what is the loaded voltage of the ECM fuse #27 while ECO algo doing its battery drain.
If at #27 fuse the voltage does indeed showed as low as ECM voltage via OBD2, something is wrong at power PCB copper trace maybe.
No way in hell a 6mm cable can drop a voltage that much while loaded only at 5-6 amps load.
If fuse #27 showed higher voltage ( it should ) than ECM voltage via OBD2, that is EXTRA HOMEWORK for me . I then need to mess with ECM wire assy , that I want to avoid.
Can you measure the voltage between F27 and engine GND to see if that clossely matches what the ECU is reporting over ODB2 PID?
measure voltage: F27 to GND
Most likely yes +/- 0.2v so the drop is upstream before power dispatch. I would go up the ladder towards the source, checking from point to point.
----- > Edt: remote sensing input for ODB2 Voltage
'litle caution in the wind:there is a considerable chance the ECU is not measuring its own power supply but is in fact sensing a different remote lead point or phoning order to F-SAM which has access to EVERY power distribution wire upfront. So SAM or ALT would be really good modules to ask, right?
How about, measure along to locate a steep drop after a large load or between ALT vs. MAIN (@V19)
That would be a good comparative to answer what power source is supplying the whole car with the A/C huming.
With ALT as source the GND path to ECU is the shortest and the best possible.
Last edited by CaliBenzDriver; 06-05-2021 at 10:10 PM.
Reason: voltage source
Yes, surely I will measure F27 voltage output, hence I need that fuse jumper,otherwise it is not safe to cruise and log that voltage.
The fact I need to find out is, how much voltage drop each connection from MR6>>F27>>ECM under heavy and long discharge using my own DMM.
It would be nice if I can back probe the ECM connector power wire from that F27 fuse, but it is a BIG risk if car is moving.
So until I can find a safe way to measure power input voltage at ECM connector while car is cruising, I have to assume OBD2 Control Module voltage is accurately representing ECM working voltage.
I doubt though that ECM voltage data is from N10/1 front SAM. Voltage data is so simple to acquire within ECM N3/10 itself.
Yes, this location is not so good and probably out of sight for most owner.
There are like 6 baby wires to this point. I do not know yet where it goes to because I cant even ID its proper name/designation.
I am still confused that my RHD E400 is so an "outcast", MB WIS often forgot about this model hahahah.
I can no more trust M276 designation, until I see M276.8 ......... otherwise it is then for the 3.5L NA.
The big cable to engine block/transmission bell housing is NOT in any W212 document I can find for grounding points.
Maybe I am still WIS/EPC dummy user . I have to admit, using WIS/EPC is nothing like using Google search engine
One last ground point recently discovered.
Probably a Left Hand Drive car will call this W16/6 grounding point. Near the brake booster ? Yikeess.
I am going to follow your lead on the GND cleaning campaign.
👍
So far I have only checked 5 points and they were all in need of attention, like the one you're showing in top post. OP distressed GND 🤣
The trouble comes from manufacturing. The posts show resisdues of wax protectant and the nuts have a significant lip of paint - The combination of both is unreliable connection with voltage drop under load.
Could you do us a big favour and show *ALL* GND points for: hood, cabin, trunk, carriage etc...
GND locator diagram
I want to rework the GND points for the VIP circuits:
SAM'S, ECU, CGW, Headlights....
I wonder what are the modules tucked away under rear seats besides mBrace??
We could start a list with all the worst GND's.
Last edited by CaliBenzDriver; 06-13-2021 at 09:26 PM.
05-29-2021, 01:58 PM
. Only can clean the other end.
. So basically that is a 51 mm2 (corrected 31 May 2021) cable/s.
