Electronic Accelerator (EA) - Who's got the best price?
 

Hi all,

I found recently that my '93 600SL needs both EA units (current dealer price $6500!). I have a lead on a company that might rebuild them, but I would like to know if anyone has a good connection on salvage, used or new modules. I would also like to know (if anyone heard a little bird say) what the actual dealer list on these units is. I'd hate to have to sell my car, but since the wholesale KBB on the car is ~$16,250, it would make little sense to spend so much to repair it. Thanks a bunch!

Justin

This post is a PRIME example of why I don't see myself in a newer MB. I'm not sure I would take one for free, because I wouldn't want to have a heart attack over it.

There should not be a SINGLE FREAKING ELECTRONIC ASSEMBLY in ANY CAR that costs that much. Or, if it does, it should come with a lifetime (and I mean life of the car, regardless of who posesses it) warranty. Maybe I'd be happy with even 20 years. This would imply that the mfr would design it to be repairable or would stock a good number of the parts at the end of the model run.

Seriously - I am aware that this was an expensive car in the first place - but this is simply over the top.

Comments?

Rebuild Cost
 

Hello again,

Well.. I did find a company that will re-build the units at a cost of $1600 each, bringing the repair to $3200. A great reduction of the $6500, but I think with all the collective resources we have we can do better.

Also, for other less expensive models I would assume a repair of half the original unit cost, which should be a boon to those with $1100 EAs.

Still looking for the best solution, and appreciate any help getting to it!

Justin

P.S.: I agree with the sentiment on the costs, especially since I'm paying them, but drive a 600, then drive any new car you could resonably afford.
Then... you have your answer!

Try the networks . . .
 

. . listed in the LINKS section (bottom of page) of my web page; I've had good luck with the PartTrackers network.

Following the EA trail...
 

JimF,

I called Beckmann, they have an even better price. The catch is, you have to know a repair center, as they will charge you full retail if you buy it personally. However, if you know a repair center that will sell it to you for cost, have them buy it, and you'll save a bunch. They told me they don't have a problem with that.

Their price on the units are:

0001415625 - $1898 Retail / $1233 Wholesale
0001415525 - $2288 Retail / $1487 Wholesale

$4186 Retail / $2720 Wholesale

I will continue to look and see what else I can come up with. My father is an electronics engineer, I'm going to have him take a peek into it and see what he thinks. He had a couple of ideas on how it might be repaired. I'm sure usually they rebuild the motor, replace the pot circuitboard and the wiring.

Justin

If you loolk . . .
 

. . . at the pictures in MENU#24, you'll see the 'pot' and how it wears. That appears to be the main culprit and there's no replacement assy, that I know of, for that part. Now with proper microelectronic facilities, they probably make a new 'pot'.

If you look at the wiring, it is as new, at least in the one I removed from my car.

Hopefully, you will impress on your dad the importance of performing testing/examining/replacing in an undetectable manner - I would not want to lose the "core charge" on these babies!

Repairing an EA.. the adventure continues
 

I read all your stuff a few days ago, JimF, and was very grateful for the pictures.

I'm assuming the people that rebuild these units professionally do have a source for a new circuitboard that has the resistance element in it. We just don't know what source that is and obviously nobody is talking.

I wouldn't either if I were rebuilding something that cost 2-300 to fix and could be sold with an +130% markup.

Porsche 944 owners apparently have a similar problem with a pot based sensor, but they have it worse, as Porsche has quit selling a replacement part! Many of those people apparently extend the pot swingarm so that the contact element crosses a slightly different section of the resistance element, which is presumably intact.

Looking at your pictures JimF, it looks like the contact element crosses the entire width of the two strips of resistance element. So that might not be a way to go.

There may be a way however to redesign the part or to rebuild or re-make the resistance element circuit board. Dad does have circuit board fabrication experience, and loves a challenge to be sure.

You're right about cores though, I'll be careful.

Justin

Jim, I noticed a repair for something or other (I forgot what it was, I read on here I think) and to fix the pot that was part of it, you just had to move the wiper to an unused area on the resistance material. Is it possible to do that on yours?

The thought of having to replace two of these things is not pleasant.

Oops! I should have read the whole thread. This is what I was talking about.

I remember reading . . .
 

someplace that an ingenious repair was made by a clever person to replace the slider-pot with a mechanical precision pot. With the right adapter, that would work very nicely. There is enough room so the challenge is to build that mechanical 'bracket' so a 'standard' precision pot could replace the present wiper-pot.

Rebuild it, and they will come.
 

I'm starting to think that's the way to go. My brother is a gunsmith and has a slew of precision machining equipment and the skills to use it. I had dinner with my dad this evening and we discussed trading the slide pot with a more conventional precision unit, as you mentioned JimF... with a little luck, and a lot of work.. maybe we can find a solution. I plan on pulling the EA's this weekend, we'll start there.

Justin

Hi Justin

I'm watching this thread with interest (as probably are many others) and am looking forward to your dad's evaluations. I'm an electronics Eng with SMD (those tiny electronic components inside) and full machine shop facilities, so if you need any help with electronic/mechanical components then just let me know.

I nearly got hold of someones failed EA unit once and was going to do similar, but alas it never materialised :(

Feel free to PM me :)

Lea

What does the EA unit do?
 

Can someone tell me what the EA unit does? My light ASR & ABS have started coming on, and thee isn't a mechanic within 100 miles. Does it effect the car's operation? Mine is a '94 320SL

Check my web . . .
 

. . .page MENU#24 for my troubles with the infamous ETA (elec throttle actuator). If you mean the EA (electronic accelerator), check out MENU#9.

Since your car is a '94, you should have the "X11/21" LED/switch combo so you can read the DTCs (Diag Trouble Codes) from the Diag Module, MENU#6. For how-to-do, check out MENU#2.

Keep track of the 'blinks' and lets us know.

this weekend is the weekend.
 

Hi all,

Didn't have time last week to pull those EA's, but will be doing it this Sunday.
I'll take pics same day and post a few somewhere.

I'd like to keep my $2700, my car needs it elsewhere =)

Justin

I believe the . . .
 

. . hard part is get the mechanical pot to precisely emulate the slider pot (Ref Pot) in ohms/inch. To explain, say that the total resistance of the Ref Pot is 10k ohms and that it this occurs in 90 degs of rotation; the pot you select will have to be a 1 turn variety where the ohms/turn match the old Ref Pot ohms in 90 degs of rotation so this pot could have a total resistance of 50k ohms.

The present Ref Pot only turns about 90 degs so the same resistance must be emulated for the throttle to attain the same position.

Anyway that is not a trivial task.

all this talk about pot, and not even in a drug forum!
 

indeed!

we'll need all the luck we can get, and since I have little, three times as much skill!

EA on eBay for $450
 

For $2800 I'll get you a compleate engine !!! :cool:
Take whatever you want..........

Too good to be true
 

Apparently he found someone to sell it to in a hurry, by the time I'd looked at that auction it had been ended without any bids.

(apparently he ended it because he took a peek inside per someone's suggestion and found the wiring damaged, and thus he cannot sell it as a good unit.)

I'd love to buy a whole engine for $2800, but unless I knew the mileage on it... I wouldn't do it. If you maintain these engines, they apparently run for the better part of forever. So I'd probably take the EAs off of it and turn it into a coffee table like that one company does.

FYI, I pulled my EAs yesterday. On the '93 600SL it's a snap, didn't even need the service manual to pull them.

They will be opened and pictures should be available after Wednesday.

EA.. the legacy continues
 

My father and I took the EA covers off today, and did some measuring about.
Our measurements are not conclusive at this point although it appears that the pot wipers each have a resistance range of 400-1360ohms.

Both wipers show exactly the same resistance range, a possible indicator of a good part (as one appears more heavily worn, but still has the same range exactly). Also, the physical appearance of the resistance elements are good.

What was incredibly obvious however, was that the wiring was history.

Large sections of insulation are missing or cracked, the wiring inside them heavily oxidized. Continuity tests show no shorts, but that is with the cable stationary and under no thermal stress. There is enough movement between the wires in the main cable and the solder joints on the small PCB that rub marks of insulation are present in the housing cap (motor side).

The two next steps being taken are:

1) make the resistance measurements with an analog meter to look for jumps or shorts in the movement range of the pots, as they are hard to look for on a digital.

2) rebuild the wiring in the main cable utilizing teflon jacketed wire, which should be a permanent fix for thermal degradation. Also to be rebuilt is the cross connect wire between the two sides of the unit.

3) inspecting the electromagnetic clutch in the mechanical section is probably a good idea as well, if there is one.

Question we were debating:

1) How does the motor control the movement of the throttle plate?

Also, the throttle plate is sprung very heavily, so I don't see the motor running all the time or it would probably overheat. Is the motor only active during certain operations (i.e. cruise control)? Does it act like a servo? does it have an internal brake? We have not disassembled the motor.

Any input anyone has would be appreciated. I should have the meter and more news on Wednesday.

Anyone who has repaired the wiring harness, I'd like to know how you handled the proprietary connector section of it.

Also, I don't think I posted the codes that were stored:

DM:
006 ISC -> EA
038 ISC -> EA

ASR:
011 Solenoid valve relay A7/3k1
017 Solenoid valve relay A7/3k1
030 CAN: No reception from EA/CC/ISC N4/1

EA:
048 Reference potentiometer, potentiometer monitoring M16/3r1
096 Starter lock-out/back-up lamp switch S16/3

Here is wiring with some simplified internals of the actuators. I'm very interested in your findings.

Glad to see you both . . .
 

. . are having fun! :) Many have said that the wiring is the biggest reason for failure of the ETA (you call it an "EA" but that's the name for an existing part called the "Electronic Accelerator; The units you are repairing are called the "Throttle Actuator").

So your step 2 will probably fix BOTH units which I'm sure you both will be glad! Save lots of $$$$.

Re 1): It won't have SHORTS but may have OPENS, that is spots that are worn and don''t make contact. The failure is an OPEN, not a SHORT in the Ref Pot.

The motor . . .
 

. . can be seen in my Menu#24: it shows that it's geared and some sort of a servo loop is accomplished so that the accelerator pedal resistance is 'matched' to the amount of throttle opening. When at null, the motor shuts off.

But the motor gets a good workout since rarely does our right foot go to sleep!

I am NOT short!
 

Yes.. opens.. that's what I meant ;)

I have pictures of the wiring:

http://www.luhrsitconsulting.com/mercedes_eta.htm

Thanks myarmar for that diagram, I'm sure that will be of great assistance when I sit down in front of them again!

I'm pretty sure (knock on wood) it's the wiring too, but I might as well rule out everything else while it's apart.

Thanks for all the input!

Justin

So... one pot is the actual, showing the driver's desired throttle position (the one attached to the linkage), while the one swept by the motor action is the one that opens the throttle to that exact position, almost like a mirror? And when not powered, the motor is not coupled to the throttle... and basically the opposing unit is slaved to the primary one, or at least depends on the output sent back to the ASR system showing the throttle position?

While measuring, I noticed that there are at least three outputs of variable resistance, two increasing from ~400-1360 and one decreasing from ~1360-400. My unit is different from yours and seems to have more paths, including more wipers and elements (at least in what I can see from your photo). I'll get some overall pictures on Wednesday to show everything.

So it seems that it is a good sign that the pots still send the same values out.

Oh... and for those of you wondering why these things are so expensive, apparently Mercedes sells their commonly used replacement parts at a premium, as opposed to most manufacturers that sell commonly used parts at a discount. My local benz dealer parts jockey told me that!

It's sort of a modified . . .
 

. . fly-by-wire system. But unlike real FBW, it doesn't have the subtle features that a airplance FBW has such as the ability to interpert the intent of the pilot and then control it without causing over-corrections that a pilot might do. Anyway a complicated system.

The pictures show the wires very clearly and while they are bad, it appears that they were not shorting to adjacent ones. But, of course, you need to replace them.

Wonder how bad the 'flying' cable is???

I have two questions nagging me about these things.

1) Is there an actual throttle cable that goes from the accellerator pedal to one of these EAs? I was wondering what that linkage was but I thought there wasn't a throttle cable.

2) What year did they stop using that horrendous insulation or do they still use it?

I'm warm already.. no insulation for me thanks
 

I just came upon two interesting things.

One, the guy who was selling the actuator on ebay, says he was told that the wiring problem went away after '95. (I'm trying to get him to send his unit to me to do some measurements, as it is a known good unit)

Two, I was reading the performance forum and went to Renntech's website, and low and behold... they sell an ASR defeat switch!

Check it out...

http://www.renntechmercedes.com/pdf/R129.pdf

Near the bottom of page 2.

Oh, and yes... there is a throttle cable.

Full Plastic Jacket
 

I have not checked the cable through. It may have opens or shorts in the jacketed section. If we can give the pot area a clean bill of health, I will desolder all the wiring and rebuild. If we can't... I'm reluctant to cut open the jacketed section, as I do not know if it will affect the re-build cost.

I'm sure they replace it as a matter of course, however I would want to call them before I take any chances.

The insulation looks so badly degraded that I wouldn't be surprised if there were shorts to the case!

The spring inside the ETA comes into action when a fault has been detected (the ASR light illuminates). The car goes into 'limp home' and the driver has to press the pedal down unnervingly further than usual to get similar speeds. The gearbox is also effected.

Past around 45% accelerator depression, the pedal will suddenly feel much heavier - that's what the spring inside the ETA is there for.

And yes, there's definitely a cable and it's used for limp home mode, so you can get to a garage should/when your wiring harness fails!

To trick the system into triggering the ASR light, place the car in Drive and increase the throttle (GENTLY) from inside the engine bay. ENSURE THE PARK BRAKE IS ON.

Looking forward to your further investigations and pics.

Nice work - Lea

wire we all here anyway?
 

I have some news:

I found a bad wire between the intermediate circuit board and the harness.
The wire is to pin 14 on the DIN style connector. I cut into the harness about four inches from the connector, and found the wire good again. It is entirely possible it is/was intermittant and the cause of the whole problem. The entire harness all the way to the connector is shot. I figured at some point the harness it would be far enough away from heat to be undamaged, but that is not the case. This means that the other side of the harness that these plug into is liable to be in similar shape.

Also,

Analog meter measurements of the pots indicate no operational problems.
Using the resistance scale, everything was smooth but the analog meters for sale today have a very compressed resistance scale, and that made it hard to be sure. We compensated by applying voltage to the pot and measuring that instead. Smooth and clean for both pots, with a 100 ohm variance between them.

In addition,

We applied power to both the motor and the electromagnetic clutch, and both are operating normally. The clutch appears to have a spring that significantly lightens the burden on the motor, that's why it isn't a problem (my prior comments about overheating). Throttle movements made by the motor and clutch are smooth and sure.

I will post more pictures of the unit and wiring soon, as well as full diagrams which include pin-outs and wire colors (the one that was posted is not correct for my car, the wire colors and numbers do not match, but all else is the same). Also I will list our test methods and equipment used.

The other side ETA is coming apart tomorrow, and I am also going to look at the car to see if these two connectors are part of the main engine wiring harness. I hope they are, that way I can take care of the whole thing at once.

I've put together a supplier list of teflon wiring and protective coverings to re-build the harnesses and by monday I'll have a gauge list and be able to order the stuff I need.

Thanks for all your help everyone, I've certainly learned a lot from all of this. I'll keep you posted on the rebuild.

Justin

Great investigative work, couldn't have done it better. Your thread will be a major savior to the masses and so please do ensure you continue posting with your findings.

Uhm, I'm interested in your spring comments as I believed it was activated part way through pedal depression when the car was in limp home. However your observations would suggest it's used to assist the motor when the system is in FBW mode. Which is also a possibility. If this is indeed the case, I wonder how the extra pedal resistance is delivered at around 45% pedal depression in limp home mode? Any thoughts?


Lea

Justin,
Here is another diagram for MY 1994. The first one was for 92 - 93, but both for W140 not for 129. I don't know if there are any differences, but I have only 140 schematics. This diagram has pin 14 used, so it maybe close to what you have.
BTW, I don't know if you noticed, the wire gauges are there - numbers before color codes are square millimeters for the wire cross section.
Here is a link to convert square mm cross sectional area to AWG:
http://www.engineeringtoolbox.com/33_731.html
Reg. Mike.
P.S. I can email you better quality pdf file, but it is too big for attachment.

Great work . . .
 

. . so far! It appears that the internal wiring IS the main culprit with the Ref Pot bringing up a strong second!

myarmar: tnx for the great M119, M120 schematics... the missing link.

Waiting for the next chapter . . .

who says men don't know how to wipe?
 

Further evidence of it being the wiring is that the DIN 14 wire is common path with a resistor and a cross harness wire going to the pot section (the wiper of one of the two pots no less).

We will get to the bottom of the motor operation/clutch, as changing the wiring to the clutch will require removal of practically everything on that side.

Two other things I noticed were that the cross harness wiring was bad on the mechanicals side, and just fine on the pot side, and the clutch wiring (it does have a heat shield over it from the factory) appears to be fine.

On another note, I located some numbers for Bosch OEM parts supply and will be getting into contact with them to see if I can source the pot section anyway, as I'm sure sooner or later it does wear out. Wouldn't hurt to have a brand new one to test anyway.

More to follow...

Justin

I don't think . . .
 

. . that you will have much sucess with "Bosch" since the ETA is designed and manufactured by "VDO"!

Also I agree that you must take it completely apart to be able to re-wire it properly. Putting the 'flying-cable' back together also will be interesting. Would be handy if you could reuse that cable but with new wires.

I think you cut the sheath but you can still re-use it after re-packing the cable by the use (mil-grade) shrink tubing to finish the job. That would work nicely.

Uh... yours is... mine isn't. It's all Bosch, as you'll see from the pictures when they are up.

Also, I found by looking at the removal procedure for the main engine harness that the male side of the ETA harness is indeed a part of it, that is good news indeed!

Here is how to take care of the potentiometers. CAIG Lab CaiLube should help. I did not use this particular product, but used the others from CAIG with great results.

Confused . . .
 

. . . what do you mean by "male side of the . . harness"???

harness the power
 

The harness attached to the ETA has female connectors; so the side attached to the main engine wiring harness would be male.

I was just saying both sides are replaceable (the main harness being readily available from Mercedes) and that is good, otherwise you could still potentially have a problem even after replacing both of your ETAs.


***UPDATE***

I have disassembled the other side (non-throttle cable) ETA. Wiring is in identically poor condition, with evidence of wire shorts visible.

The unit is almost completely apart, throttle plate and shaft removed, pot assembly loose (wires not unsoldered yet), throttle return spring removed and the top half of the clutch ass'y. I need a fairly large slot screwdriver in order to finish removing one of the throttle plate stops, as it blocks removal of the bottom half of the clutch. I should have that by tomorrow so I can complete the disassembly.

FYI: ALL SCREWS IN THIS ASS'Y ARE THREAD LOCKED, EITHER CHEMICALLY OR MECHANICALLY. They are a pain in the rear to remove, make sure you have all the proper size tools or you WILL break a tool or the part. On top of that.. be extra careful.

Yes, now I understand . .
 

. . what you said but it would be much clearer to readers if you used more correct terms so most could easily understand. Not criticizing but trying to get you to use 'standard' terms.

The cable that is permanently attached to the ETA's metal body is called a 'flying cable'; the term coming from the fact that it's not removable (as are most cables) and that it 'sort-of-flys-around' because it's captive.

The END of the cable's connection (male or female) does not define the cable's function. As you noted, it's female but that has nothing to do with the cable's definition.

Yes, I understand that car's portion of the cable, rightly called part of the wiring harness, is also probably in the same condition as the 'flying cable' . . . but maybe not.

For my car that portion of the cable runs along the top of the fenders and then into the F23 module box. The heat is MUCH lower there and just maybe it's not bad. But if your engine harness has never been changed, that's wishful thinking and you will have another job after rebuilding the ETA. Oops, that's two ETAs!

The Update, Part 1
 

Alright everyone,

High res pics of (almost) everything!

http://www.luhrsitconsulting.com/mercedes_eta.htm

I've got some hot leads I'm working on, so more to follow!

Justin

Man, that looks like a goodly amount of work, good job and great pics.

Mercedes should be ashamed of themselves for using wiring that decomposes like that. :pukeface:

I looked at both of my EA's and neither appears to have a throttle cable attached; did they change by 1997? What side is the actual throttle cable on yours?

One thing I've been thinking of, is it possible to remove both motors and have a physical cable to the butterfly valves? It looks like the potentiometer is attached to the butterfly shaft so it appears the computer would still get a valid throttle position value from it. This would obviously eliminate the ASR control of the throttle but I wonder how well it would work if it is even possible????? It would be nice to have complete control of the throttle. :D

Butterfly..
 

It's probable that Mercedes moved to a full e-throttle by '97, which would explain why you don't have a cable. Ours is attached at the drivers side unit.

Due to a lack of space, it would be a harrowing task to try and rig throttle cables on the other unit. So much work it couldn't possibly be worth it!
You'd basically be redesigning fully at that point!

Given enough time and effort it could be done one way or another.
But you'd better have some German engineering blood in you!

Justin

Given the condition of the wiring, it's amazing that M-Bs of this era don't simply spontaneously combust. If I owned one I sure as heck wouldn't park it in my attached garage!

Whoever signed off at the factory on using this insulation has probably been removed from the building and shot.

Your pictures certainly . . .
 

answer that possiblity I posed. Hard to believe that the internal wires can deterioate so badly inside a 3/16" (or so) thick cable insulation.

I never took my flying cable apart but I will just to see if it's as bad as yours. No wonder they don't work.

GREAT pics Justin by the way, thanks

There are many reasons why the butterfly is electronically controlled; idle RPM control, cruise control and driving experience - this is simply a non-linear power response with respect to pedal position. Makes for gentle cruising when accelerator is within it's first 20% of travel.

Disabling the ETA system and connecting cables direct to the butterfly in my opinion is really a big no-no!

Keep the info coming Justin - we all owe you a large beer or two ;) :D :sun_smile

Lea

I was just throwing that out as a possible option to spending a couple grand on the EAs. Although I would actually prefer to have complete control of everything with the only computer controlled system being the ABS. Who knows though, all of these systems might save my life someday.

It would be cool to mash the throttle and get instant WOT :D even though if you know the system, you can get most of what you want with careful throttle application.