Electronic Accelerator (EA) - Who's got the best price? - Page 3 - PeachParts Mercedes-Benz Forum

Justin_Luhrs · #31 01-26-2005, 11:00 PM

Quote:

Originally Posted by JimF

. . 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 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.

LeaUK · #32 01-27-2005, 05:52 PM

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

Justin_Luhrs · #33 01-30-2005, 01:09 AM

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.

LeaUK · #34 01-30-2005, 03:58 AM

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

myarmar · #35 01-30-2005, 09:52 AM

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.

JimF · #36 01-30-2005, 12:27 PM

Quote:

Originally Posted by Justin_Luhrs

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.

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.

. . 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 . . .

Justin_Luhrs · #37 01-30-2005, 01:27 PM

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

JimF · #38 01-30-2005, 04:13 PM

Quote:

Originally Posted by Justin_Luhrs

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.
Justin

. . 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.

Justin_Luhrs · #39 01-30-2005, 04:23 PM

Quote:

Originally Posted by JimF

. . 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!

myarmar · #40 01-30-2005, 10:30 PM

Quote:

Originally Posted by Justin_Luhrs

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.
Justin

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.

JimF · #41 01-31-2005, 12:18 AM

Quote:

Originally Posted by Justin_Luhrs

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!

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

Justin_Luhrs · #42 01-31-2005, 12:46 AM

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.

JimF · #43 01-31-2005, 01:56 AM

Quote:

Originally Posted by Justin_Luhrs

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.

. . 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!

Justin_Luhrs · #44 02-02-2005, 10:36 PM

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

leejxxxxx · #45 02-02-2005, 11:27 PM

Quote:

Originally Posted by Justin_Luhrs

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.

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.