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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| How-to instructions for modifying the diff locker switch box
There was some discussion a while back about modifying the switch pack so that you can engage the lockers in any sequence you like. A few of us on this board have had a go at it with mixed results.
I decided to get all scientific about it, and made up a test jig so I could test out the switch pack on my workbench, instead of in the Gwagen. Sean Pillyaw got me some connectors (and generously donated them to the cause), and RadioShack had the rest of it.
I finally got round to looking at the boards today (it was 107 degrees outside, so I was forced to stay in). I think I've figured out a way to do the mod that is pretty manageable for most people.
I'll do a full write up later of what I found out, but for a first installment, here's a link to all the instructions you'll need for modifying the switch pack. Once you do this mod, you can engage any locker any time. You don't have to wait for the center to come on first etc.
http://web.mac.com/rgrussell/Geezer/Diff_Lock_Switch_Pack.html
I'd suggest you only do this if you are fairly handy with a real fine soldering iron and have some good light and magnification.
Let me know if you have a go at it.
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UN Mobile
Date registered: Dec 1899
Location:
Vehicle(s):
| RE: How-to instructions for modifying the diff locker switch box
A very nice and detailed write up, in your probing of this system did you notice how the the computer is signaled to turn off ESP, ABS, BAS etc. I have heard that exposing pin 7 on the plug to either ground or 12 volt would turn the computer off. Can you confirm this and wether 12v or ground.
My 2002 ESP is a real pain and have been considering to do something about it. Ideally I will mount a 3 position rotary switch on the dash labled ESP: "high" the current and way to sensitive setting, "LOW" the setting that is set when the ESP OFF switch is on the dash is pressed I believe that this is a momentary contact switch that resets all functions to a lower value but the functions return to the their normal setting above 38 mph and "OFF" a real off maybe using pin 7 of the locker cluster. |
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: How-to instructions for modifying the diff locker switch box
Yes, I did take a look at that. I had the same plan!
It turns out the the theory about pin 7 is not correct for all models of Gwagen. On G500 models pin 7 is not connected to anything in the vehicle. There is not even a pin in the connector for it.
In fact there are two separate disable circuits.
Pin 4 is the ESP disable output from the diff lock switch pack to the ESP unit. It disables the ESP when any locker is selected (ie any yellow light is on). It does this by pulling Pin 4 to ground. The ESP unit disable input has an internal pull-up resistor holding it at 12V.
Pin 8 is the ABS disable output from the diff lock switch pack to the ABS unit. It is disables the ABS when any locker actually engages (ie any red light is on). It does this by pulling Pin 8 to ground. There is no pull up resistor in the ABS unit, it is in the diff lock switch pack. So if you remove the switch pack, the ABS alarm comes up in the dash display, but the ESP alarm does not.
The ESP disable is a "hard" disable. The ESP will not come back on when you go over 40mph like it would if you had pushed the ESP button on the dash. I believe there are only two conditions for the ESP - either on or off. I don't think there is an intemediate soft setting.
So if you wanted to install a "hard off" switch for the ESP, you could just wire a switch from Pin 4 to ground.
You could also install an ABS disable switch on pin 8 (I need to check you can just pull that low without blowing up the output when its high). That way you could avoid having to engage the center diff on loose gravel roads just to turn off the ABS, which is what I've been doing.
Someone who is even more obsessive-compulsive than I am might like to look into the unused rocker switches to either side of the red hazard light warning switch. It would be cool to use those for ESP and ABS disable. Better than Radio Shack toggle switches shoved through a hole. On the G500, they are mechanically disabled, but on other models of Merc, eg C-class, they are mechanically enabled. So it must be possible to buy the little plastic bits to make those switches work. You'd probably only have to spend three weeks on the phone to Germany to sort all that out. Please post it here afterwards!
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: How-to instructions for modifying the diff locker switch box
Todd,
question: Why is your ESP a real pain? What is it doing? |
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diehardg
Veteran
Date registered: May 2006
Location: Tokyo, Japan
Vehicle(s): 2000G500L, 2015 G350BT, 2016G63(now), 1968 S404
Posts: 220
| Re: How-to instructions for modifying the diff locker switch box
My ABS is disabled by just unplugging ABS sensor wire. Connectors are under the hood. If you trace it from front knockle, you'll find small a plastic connector. Mine is always off but if you put a switch, I think you can turn ABS on/off from inside.
Yasu |
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: How-to instructions for modifying the diff locker switch box
Richard,
I am nominating you for the G Oscar!
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| Re: How-to instructions for modifying the diff locker switch box
Yasu is correct about the ABS switch. Put it in series with Pin 8, and that's it.
Someone asked me why you would want to do this mod.
There is one important reason that is not obvious. The first time I needed my lockers, they didn't work, and I got stuck in the middle of nowhere in Mexico and spent all day digging out of sand. When I got home, I found that the contact for the center-lock sensor switch was intermittent. Each time the contact wiggled, the switch pack would think the locker had dropped out, and it would remove power from the rear locker, which would drop out and remove power from the front locker. Each time this happens the vacuum in each line is lost, and so the end result is that the lockers would not stay on properly. This seemed to me like a design defect - you lose front and rear lockers just because of a dirty contact on the center diff sensor. I only noticed it because I could hear the vacuum solenoids chattering in and out intermittently.
With this mod, you can engage any locker regardless of whether the sensor switches are working. That is the main reason for me. It makes the system much more reliable. There are already too many things to go wrong in the G500 locker system (electric-over-air-over-hydraulic) without adding more reasons for it to not work in the switch pack.
I'll let Harald explain the side benefits of using the lockers individually! |
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GwagenLover
Extreme Veteran
Date registered: Apr 2006
Location: Winston Salem, NC USA 27104
Vehicle(s): 2016 G550 & 2016 GLE350
Posts: 473
| RE: How-to instructions for modifying the diff locker switch box
Could you experienced guys go one step further and put pictures and locations of thes pins and plugs you are speaking of? |
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: How-to instructions for modifying the diff locker switch box
GwagenLover - 6/23/2008 12:12 PM
Could you experienced guys go one step further and put pictures and locations of thes pins and plugs you are speaking of?
When you remove the diff lock switch pack from the dash, you will have to pull the connector off the back of it to get it out. You can makes all the connections to the wires that come out of that connector. Here's a photo showing the wires you need...
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GwagenLover
Extreme Veteran
Date registered: Apr 2006
Location: Winston Salem, NC USA 27104
Vehicle(s): 2016 G550 & 2016 GLE350
Posts: 473
| RE: How-to instructions for modifying the diff locker switch box
Now we are getting somewhere.  |
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hipine
Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
| RE: How-to instructions for modifying the diff locker switch box
All this talk of manually disabling safety systems got me thinking... In the regular factory configuration, is there something like a speed-related lock-out that prevents you from engaging the lockers at higher speeds or anything? Electrically disabling the ESP because it's misbehaving is a modern equivalent of the electrical tape over the oil pressure light trick, or turning up the radio when the engine starts knocking. Treating the symptom, not the disease. -Dave G. |
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: How-to instructions for modifying the diff locker switch box
hipine - 6/23/2008 3:03 PM
In the regular factory configuration, is there something like a speed-related lock-out that prevents you from engaging the lockers at higher speeds or anything? Electrically disabling the ESP because it's misbehaving is a modern equivalent of the electrical tape over the oil pressure light trick, or turning up the radio when the engine starts knocking. Treating the symptom, not the disease. -Dave G.
There's nothing to prevent you engaging the lockers at any speed. The control box doesn't know anything except which buttons you pressed and which lockers are already engaged. I've engaged them and disengaged them at high speed just to check. No problems at 70mph. You need to be sure you won't be needing to do any steering before you try it.
You are probably right about disabling the esp being a bad idea. It's there for a reason.
Regarding the ABS, there is legitimate reason to do that. If you are on a loose surface, you stop quicker without ABS, because you push a pile of dirt in front of the locked wheels. With the ABS on, the wheels unlock repeatedly and prevent the little mountain of dirt building up. It makes a big difference, I've done some unintentional experiments. On some types of loose road, you can barely stop at all with ABS, you just eventually run out of forward momentum a quarter mile down the road.
I agree with your concern though. You should never do a modification that makes things worse. You see a lot of that at the weekends in SoCal deserts.
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blackbox
Date registered: Dec 1899
Location:
Vehicle(s):
| RE: How-to instructions for modifying the diff locker switch box
would you be interested in coverting my rockers for a fee? |
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fernweh
Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
| RE: How-to instructions for modifying the diff locker switch box
Thank you Richard,
I have my spare locker switch assembly already on my desk and looking now for good glasses.
Great step by step instructions to do this deed 
My ABS is off right now on my own doing, but the point of disabling the ESP by its own is just great....... 
Dave G. doesn't know how it feels to be pulled suddenly into the oncoming traffic while doing a very easy turn to the right, a bit downhill and just cruising with ~40 mph - by the ESP computer 
Now we need to find a nice place for the ABS and ESP OFF switch......
Thanks again for your hi-tec work,
Karl |
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W5YK
Extreme Veteran
Date registered: May 2006
Location: San Diego
Vehicle(s): 2002 G500, Unimog U2450,
Posts: 543
| RE: How-to instructions for modifying the diff locker switch box
blackbox - 6/23/2008 5:15 PM
would you be interested in coverting my rockers for a fee?
I will mod anyone's control unit if they make a $50 charitable donation here...
http://www.franklinfoundation.ca
PM me for my shipping address. I'm in San Diego. You ship it to me, I will pay to ship it back if US/Canada.
Note that you will have no ABS for a week while I do it, and lots of ABS alarms in the dash display. |
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: How-to instructions for modifying the diff locker switch box
Dave,
there are some (off-road) situations where ESP would not be helpful
for that we have the ESP off switch (works up to 40 mph)
When any of the lockers is activated the computer does not get the needed values to control ABS, ETS, ESP and others and therefor the locker switch deactivates those systems.
So, aside from the lack of individual on/off for the lockers (and Richard solved that problem for us) anyone using the 463 for off-road should be happy with what's provided.
But there are others not so happy with the ESP.
MB engineers have created an ESP software program for the G that is fairly conservative taking weight, stock tires and high CG into consideration.
The software is so conservative that aggressive drivers will experience frequent ESP interferences. They would love to have an off switch. Bad approach considering the added safety provided by ESP (even the best driver can not outsmart ESP!).
And then there are those who have mounted larger tires. Their effect on ESP can be adjusted by going into the vehicle software. But if the achieved new setting is only a couple of miles off (a perfect software adjustment is unlikely due to the many different tire sizes) ESP reactions can be annoying as well. Turning ESP off in that case would not be smart either. |
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Fernando BR
Date registered: Jan 2007
Location: Brasil
Vehicle(s): G500/05 300GE/91 300GD/80
| Re: How-to instructions for modifying the diff locker switch box
Harald,
I never offroad at more than 40 KM/h in trails , so if sometimes i want the confort of 4ETS i left center lock off. If i am on sand or in a place where i can go up 40km/h or I do not want 4ETS and want to control i will actvate center diff to have effective 4x4 ( 80% of the time offroad) .Rear I turn on and off all the time , front 99% of my offroad is off.
But a question come into my mind : If in a 463 front diff is engaged in a independent way ( center diff unlock) 4ETS /EPS....still on? If yes , EPS swicth off will be really needed.......or a confuse situation will be on , so to do not have lock order, NEW EPS SWITCH will be mandatory.
I never use ABS off switch in my 300GE.
Edited by Fernando BR 6/24/2008 1:44 AM
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ewalberg
Expert
Date registered: Apr 2006
Location: Past: San Francisco. Present: Germany
Vehicle(s): 2000 g500
Posts: 1887
| Re: How-to instructions for modifying the diff locker switch box
Just to correct that g500's don't have pin 7, based on W5yk's observations it sounds more accurate to say any truck with ESP doesn't have pin 7, instead it has pin 4 and pin 8. In pre ESP trucks (whether this is true for the very few 01 trucks with the new interior and no ESP i don't know) but in the older interior trucks including those with updated steering wheel, pin 7 is the active pin. It acts like pin 4 for the newer trucks in that it disables the system any time you have a yellow or red light on on... not just red... (locker botton pushed or locker locked or ABS kill pushed and Pin 7 is grounded) and ofcourse it's only acting on the ABS system since there isn't any ESP. I think i'm probably responsible for all the hoopla trying to ground pin 7 to kill ESP when people were looking for solutions.
One intersting and i think very cool side affect of your observations about the pins, is that they (ESP and ABS) are in fact separately managed so you could leave on ESP and turn off ABS so you could carry your speed offroad and still stomp the brakes for fast stopping, but still have the benefits of ESP off road. Or you could turn off ESP on road and keep ABS on while on road. Which would be my preference. I'm sold on ABS off while offroad for braking, but harald had a good story on how ESP can benefit offroad too... especially when trailering... although i don't trailer.
It sounds to me like Fernweh may have had the same experience i've heard from UnMobile and another fellow on the board (at the meeting in Collie Autoworks) where the ESP really agressively grabs the outer tire and pulls you straight in circusmstance that appear totally inappropriate (non-evasive maneruvers) and where the only reason the trucks intervention didn't cause accidents were because it was NOT an evasive maneuvers (where you could afford to have the truck not go exactly where you needed it to, or to fight you as the case may be).
Considering i've yet to need ESP (no accidents) and i've done at least 3 evasive maneuvers during ownership that would have scared the living crap out of anyone had i had passengers at the time, i simply can't imagine the system would not have kicked in and pulled me straight to my trucks demise, or to the demise of some poor folks in a carolla... i don't care how many lives it's saved, i'm glad it's not in my truck becuase having my trajectory changed by more than a foot or two in at least 3 instances would had dire consequences.
I know it's easy for me to say since i don't have it, and it is proven to help often and in many cases, but thinking it doesn't add risk in some way or another is fool hardy at least in our trucks case, and if you chose to not understanding how it can add risk and making your own determination on what risks you want to take is up to you... but as far as i'm concerned, the only reason i haven't injured my truck, myself, or anyone is because i'm without it. And i'm not saying it doesn't belong in the truck for many drivers, i've even said how i'd be interested to use it, but it still doesn't change that i'm happy to not have it with my normal driving, and it doesn't change that i think they've set the bar so low for trigger (At least in some trucks based on statementes here) that i think it adds more risk that it would if they set it more realistically with how well the vehicle actually behaves... and for those that think i'm some speed demon driver, i haven't had a speeding ticket in more than a decade becuase i just don't drive very fast.
i know my satisfaction at not having it is off topic, but it's realistic to assume i might end up in a newer truck some day, and i'm just glad to read there's a way of switching it off... so that's what got me started anyway.
To go sort of back on topic, UnMobile, didn't you say you had a nearly catastrophic failure of your ball joints on your steering rods at pretty low mileage? I remember we speculated that it could have been speed along by all the stress of having the whole truck stopped by brake force applied through only 1 wheel, much like the added stress of a truck with lockers on axles not designed for it... car steering systems not generally being designed to handle the stress of max brake power going through only one tire... traditionally being distributed through all tires... and where brake forces are pretty much always higher than gas pedal related forces (at least on things like steering and non-direct power train). The reason this is more on topic is for people with ESP if they've had that sharply jerking ABS, to keep an eye on their steering linkages for slop... it's something to do in anycase on any truck, but this is a new and greater stress on the system than non-equiped trucks. Yeah, this could sound like i'm gloating, but i check mine occasionally too, and frankly, i'll take someone thinking i'm gloating if it helps some other fellow keep an eye on out his trucks underpinnings. No harm in that. 
Edited by ewalberg 6/24/2008 4:43 AM
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roughneck
Expert
Date registered: Apr 2006
Location: UK, Germany & USA
Vehicle(s): 270 cdi.300 GD 300 GE.lwb 300 GE.swb. Disco 2
Posts: 4398
| RE: How-to instructions for modifying the diff locker switch box
A wonderfully engineered solution, However I have seen this done in a much simpler way using the existing switches in situ.
A shunt from the centre switch power input to both the rear and front switches power input enables selection of diff locks individualy and not in a sequence..
Edited by roughneck 6/24/2008 5:00 AM
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| RE: How-to instructions for modifying the diff locker switch box
roughneck - 6/24/2008 1:53 AM A wonderfully engineered solution, However I have seen this done in a much simpler way using the existing switches in situ. A shunt from the centre switch power input to both the rear and front switches power input enables selection of diff locks individualy and not in a sequence.. The fix you describe sounds like it is meant for the previous incarnation of the W463 locker switches. Those switches were mechanical. This set is electronic. The "switches" on the later (and current) design are just momentary push buttons that feed into a ~1980's era discrete digital circuit board. The logic on the circuit board is what defines the order of operation. The fix changes the logic.
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