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  #16  
Old 06-10-2017, 04:43 PM
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Quote:
Originally Posted by ROLLGUY View Post
Does the odometer portion work? I am not sure exactly how the odometer and speedometer interact, but for sure the odo is driven buy gears, and they do go bad. Does the same motor, servo or whatever it is called operate both?
There is a separate little motor I believe that turns the little gears. The gears are broken so the odo doesn't work

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  #17  
Old 06-10-2017, 10:56 PM
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Originally Posted by dude99 View Post
Have you checked the OVP relay? Does the tach still work?
I have not checked the ovp relay yet. The tach does work after I bypassed the signal through the egr control module.
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  #18  
Old 06-11-2017, 05:11 AM
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Trevor Hadlington
 
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Whats the use of a speedo cable if its electronic .The cable is not turning ,The poster as fitted 2 other speedos to the car that are the same, so ,, take it for a spin and look at the cable simple ..see if it turns . I have repaired 4 of these W124 and W123 and i have never come across a motor inside yet.
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  #19  
Old 06-11-2017, 05:32 AM
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Trevor Hadlington
 
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Just been reading about the speedos for this car , and shure enough as above post they did make some fully electronic speedoes in 1981-2 .And after a time they went back to manual cable drives But i have never seen one of the electronic types speedos . The cause of most problems with the gears , is setting the oddo on the move .
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  #20  
Old 06-11-2017, 05:37 AM
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Trevor Hadlington
 
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speedo

This is the speedo head and how to remove the drive cable fron gearbox ..
Attached Thumbnails
Speedometer help-mom.jpg   Speedometer help-engine-removal-disconnect-speedo-cable.jpg  
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  #21  
Old 06-11-2017, 05:38 AM
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Trevor Hadlington
 
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And all the information i found about this is sitting on this forum .Just do a search .
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  #22  
Old 06-11-2017, 07:05 AM
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Quote:
Originally Posted by optimusprime View Post
Whats the use of a speedo cable if its electronic .The cable is not turning ,The poster as fitted 2 other speedos to the car that are the same, so ,, take it for a spin and look at the cable simple ..see if it turns . I have repaired 4 of these W124 and W123 and i have never come across a motor inside yet.
Please stop arguing about a chassis you have no experience with.

The S class w126 is all electronic.

The cable is wires, not z spinning cable.
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  #23  
Old 06-11-2017, 07:07 AM
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Op...
There is a power connector under dash above accelerator that must be plugged in...
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
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  #24  
Old 06-11-2017, 09:21 AM
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Originally Posted by vstech View Post
Op...
There is a power connector under dash above accelerator that must be plugged in...
Hmm there is good chance it has come unplugged after I replaced the expansion valve. I'll look around for any connections.

Also I checked the ovp and it is working fine.

Edit: I'm not sure if this is relevant but my tach takes a few seconds after startup to actually work.

Last edited by Ncbenz; 06-11-2017 at 11:10 AM.
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  #25  
Old 06-11-2017, 09:37 AM
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I took a quick look and didn't see any loose connectors near the accelerator.
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  #26  
Old 06-11-2017, 11:41 AM
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Quote:
Originally Posted by optimusprime View Post
Just been reading about the speedos for this car , and shure enough as above post they did make some fully electronic speedoes in 1981-2 .And after a time they went back to manual cable drives But i have never seen one of the electronic types speedos . The cause of most problems with the gears , is setting the oddo on the move .
All 126 chassis were electronic. It would be nice if people stopped arguing and paid attention. If you don't know what you're talking about, please stop putting out incorrect information.

There is no speedometer cable in a 126. They did not "go back" to using one either. The OP is having an electronic issue of some sort, plain and simple. The challenge is finding out WHERE the electronic problem is. Bickering about cables that don't existing on the car is progressing the discussion nowhere.

OP- See the attachments for a diagram of where your speedometer is getting power/ground/signal from.

Last edited by Diseasel300; 06-19-2021 at 10:06 PM.
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  #27  
Old 06-11-2017, 02:51 PM
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Hey Ncbenz,

If you would like to have your speedometer/odometer tested/inspected/repaired I would be happy to help out. I can bench test the unit for you and probably help you narrow down the problem.

I've seen a number of problems on these units including capacitor failures, fuses blowing (some model unit do have a small fuse built in), resistors getting hot and failing.


Just thought I'd chime in and make the offer!

--Kris
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  #28  
Old 06-11-2017, 03:28 PM
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Originally Posted by JamesDean View Post
Hey Ncbenz,

If you would like to have your speedometer/odometer tested/inspected/repaired I would be happy to help out. I can bench test the unit for you and probably help you narrow down the problem.

I've seen a number of problems on these units including capacitor failures, fuses blowing (some model unit do have a small fuse built in), resistors getting hot and failing.


Just thought I'd chime in and make the offer!

--Kris
Hey thanks man. I'm going to try to exhaust some more testing but more than likely I will have to take you up on that.
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  #29  
Old 06-11-2017, 05:45 PM
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I recently drove my electronic speedo on the bench. 1982 300sd is electronic and required a signal generator and 12v power supply.

Details here

Fixed 1982 300SD odometer slip at high speed

Getting it up and running on the bench was priceless for troubleshooting. My problem was in the stepper motor portion of the speedometer (that is the odometer I guess).

a drill won't work on this style of odometer.
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  #30  
Old 06-11-2017, 06:06 PM
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Here is the schematic for the Speedometer. Page 120/2
https://www.startekinfo.com/StarTek/outside/12253/program/ETM/126td83-85.pdf

I noticed the impulse generator picks up a ground behind the instrument cluster. Usually grounds are where many of the electrical problems come from. Have you looked at the transmission end of things?

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