300 CD speedo and odometer cable - Mercedes-Benz Forum

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 13 (permalink) Old 05-20-2014, 07:46 AM Thread Starter
BenzWorld Member
 
cargirl's Avatar
 
Date registered: May 2010
Vehicle: 1980 300CD
Location: Clarks Summit PA
Posts: 51
Mentioned: 0 Post(s)
Quoted: 8 Post(s)
(Thread Starter)
300 CD speedo and odometer cable

I have a 1980 300CD - when I bought the car the odometer was not working and now the speedometer has stopped. I have to get it fixed in order to pass inspection. Can anyone tell me if I am ordering just one cable to fix both problems? The mechanic I am using does not seem to have the time to help me figure this out so on top of the inspection problem I need to find a new mechanic (I am near Scranton PA if anyone has any suggestions). In the meantime what am I looking for to fix my odometer- speedometer problem.
cargirl is offline  
Sponsored Links
Advertisement
 
post #2 of 13 (permalink) Old 05-20-2014, 08:59 AM
BenzWorld Member
 
Date registered: Apr 2014
Vehicle: 1982 300CD
Location: So. California
Posts: 50
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
These speedometers are known for problems. Based on the fact that your odometer stopped working first and then later the speedometer (MPH), I don't believe the problem is with the speedometer cable but rather the speedometer itself. They can be repaired but the speedometer will need to be removed from the car and the cost to repair the speedometer is around $150 (does not include removal or replacement in the car). The other option you have, if you do not care about the number of miles recorded on the car is to find a used but working speedometer. Just make sure the used speedometer has been tested and both the odometer and speedometer work properly.
BWhitmore is offline  
post #3 of 13 (permalink) Old 05-20-2014, 09:13 AM Thread Starter
BenzWorld Member
 
cargirl's Avatar
 
Date registered: May 2010
Vehicle: 1980 300CD
Location: Clarks Summit PA
Posts: 51
Mentioned: 0 Post(s)
Quoted: 8 Post(s)
(Thread Starter)
I am confused. The speedometer and the odometer are connected in some way? Your suggesting I either by a new speedometer or fix the one in the car? What I really need is a good mechanic that I can trust to do this for me and not charge me an arm and a leg. It has been suggested on this forum that I shouldn't own a 300CD if you can't do the work yourself because it will be too costly. True enough. I have 6k into this car but don't regret a penny. Every thing that has ever needed to be done has been done. But then I moved and lost the mechanic I trusted.
cargirl is offline  
post #4 of 13 (permalink) Old 05-20-2014, 09:24 AM
BenzWorld Member
 
Date registered: Apr 2014
Vehicle: 1982 300CD
Location: So. California
Posts: 50
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
The speedometer, odometer and trip odometer are all part of the same unit in what is called the speedometer head. The speedometer cable is a separate unit. The speedometer cable attaches to the back of the speedometer and runs down to the transmission. The transmission has a gear that turns the cable which in turn turns the mechanism inside the speedometer head and makes the odometer, trip odometer, and MPH needle work. If you have some mechanical skills and some hand tools (a 10mm wrench) I can walk you through the steps to remove the speedometer head for testing and also how to check your speedometer cable. Let me know.
BWhitmore is offline  
post #5 of 13 (permalink) Old 05-20-2014, 09:33 AM Thread Starter
BenzWorld Member
 
cargirl's Avatar
 
Date registered: May 2010
Vehicle: 1980 300CD
Location: Clarks Summit PA
Posts: 51
Mentioned: 0 Post(s)
Quoted: 8 Post(s)
(Thread Starter)
I am laughing so hard. In between posting to you on the site I am trying to put together a push mower just out of the box to mow my lawn. I would be more inclined to pay your airfare to PA to give my car a good once over. But seriously I think I may take you up on helping me with the speedometer. I would love to be able to do minor work on my own car. I will be back to you as soon as I get the mower together and finish my lawn. I really appreciate the offer.
cargirl is offline  
post #6 of 13 (permalink) Old 05-20-2014, 12:43 PM
BenzWorld Member
 
Date registered: Apr 2014
Vehicle: 1982 300CD
Location: So. California
Posts: 50
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
In order to remove the speedometer you will need to remove the instrument cluster. Tools need will be a 10mm wrench, a wire coat hanger, and a roll of masking tape and pen for marking, a pair of pliers and a pair of wire cutters (commonly called diagonal cutters or "dikes"), Phillips head screw driver.

From the wire coat hanger cut off a piece of wire about 8" long. Form a curved hook at the end of the piece of wire using the pliers.

Insert the hooked end of the wire between the end of the instrument cluster and and dash (left or right). Insert the wire as far as you can with the hooked end pointing in the direction to grab the instrument cluster on one end. Be sure to insert the wire far enough because if not inserted deep enough you will pull on the clear plastic instrument cluster face and pull it off which will then require gluing the clear plastic face back on.

After you pull out either the left or right side of the instrument cluster about 1 inch, repeat the same procedure on the opposite end of the instrument cluster until you have pulled out the cluster enough for you to get your hand behind the cluster on the right side.

Reach behind the instrument cluster in the middle at the back of the speedometer head. Unscrew the speedometer cable from the back of the speedometer head. The cable is attached with a silver color nut (the nut is not like a regular nut but is the type you can turn with your fingers). If you are unable to loosen the nut with your fingers you will need to use the pliers to loosen the nut. Once loosened pull the speedometer cable away from the speedometer head.

You will now be able to pull the instrument cluster out another 4-5 inches. Using the masking tape mark all the wires so you know where they go back. The only wires that will not need to be marked are on the left back side of the instrument cluster. There are about 10 wires that are grouped together and they cannot be mixed up. They get plugged back in only one way, there is no chance to mix these wires up when re-connecting. The wires on top of the speedometer head are removed by pinching the black wire terminal between your fingers and pulling the wires away. The remainder to the wires just pull out from the instrument cluster.

Using the 10mm wrench remove the oil pressure tube from the back of the instrument cluster. The tube has a nut where it enters the back of the instrument cluster. Turn the nut to the right in order to remove the tube. DO NOT START THE CAR WITH THe OIL TUBe REMOVED. To do so, will destroy your engine and you will have oil all over the inside of your car.

The instrument cluster can now be removed completely from the car. Take a picture of the back of the cluster for reference when re-assembly.

The instruments can now be removed one by one from the back of the instrument cluster. There are 3 separate gauges that will need to be removed. Before removing the instruments you will need to remove the small white lighting reheostat at from the bottom of the cluster. It is removed by removing the single Phillips head screw inside the white reheostat and pulling up on the reheostat.

Once all three of the instruments have been removed, take the gauge that gas oil pressure/temperature/fuel gauge and place in back in the dash opening where the instrument cluster goes and REATTACH the oil pressure tube to the back of thus gauge. Tighten the oil pressure tube with the 10 mm wrench. It is OK now to start the engine. The gauge will temporarily rest in the dash opening with no harm.

Take the car on a short drive and look at the end of the speedometer cable through the opening in the dash. The small cable inside the black speedometer cable housing should turn as you are driving. If the cable does not turn, you have a broken speedometer cable. If it does turn you have a broken speedometer head that will need to be repaired or replaced with a good used one.

Once you have determined where the fault likes, re-assembly us opposite dis-assembly. The large group of wires on the left side will only plug in one way. Look at the back of the instrument cluster on the left side for about 10 + or - pins and you will see the way that the wire plug can only go in one way. Make sure the oil pressure tube is tight and hook up the remainder of the wires according to your reference masking tape. Push in the instrument cluster into the dash opening about half way and then reconnect the speedometer cable to the back of the speedometer head. Once this is accomplished, push the instrument cluster completely into the dash opening. It is held in place by friction.

I hope this helps, let me know if you have any problems. REMEMBER, do not start the car with the oil tube dis-connected. Bill Whitmore
BWhitmore is offline  
post #7 of 13 (permalink) Old 05-20-2014, 12:55 PM Thread Starter
BenzWorld Member
 
cargirl's Avatar
 
Date registered: May 2010
Vehicle: 1980 300CD
Location: Clarks Summit PA
Posts: 51
Mentioned: 0 Post(s)
Quoted: 8 Post(s)
(Thread Starter)
What's a 10mm wrench? No I'm just kidding. But by the end of those instructions I was having heart palpitations. It just took me four hours to put a handle on a lawnmower. However those instructions are incredibly detailed - I will ask a mechanically gifted friend to do this for me and keep you posted. Thank you so much. And if you know anyone that can work on an older Benz in the Scranton, NY, Philadelphia area please let me know. Again, thank you for the awesome instructions.
cargirl is offline  
post #8 of 13 (permalink) Old 05-20-2014, 01:14 PM
BenzWorld Member
 
Date registered: Apr 2014
Vehicle: 1982 300CD
Location: So. California
Posts: 50
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
I am in Southern California and know no one in New York or Pa. You might want to check to see if you have a local chapter of the MBZ Club of America in your area. One of their members can probably refer you to a good mechanic in your area.
BWhitmore is offline  
post #9 of 13 (permalink) Old 05-20-2014, 02:03 PM Thread Starter
BenzWorld Member
 
cargirl's Avatar
 
Date registered: May 2010
Vehicle: 1980 300CD
Location: Clarks Summit PA
Posts: 51
Mentioned: 0 Post(s)
Quoted: 8 Post(s)
(Thread Starter)
Would it make sense to buy the head and the cable before I remove the instrument cluster so I can fix the problem right then and there. And what about the odometer - I am not sure if that is needed to pass inspection but I would like to have it fixed.
cargirl is offline  
post #10 of 13 (permalink) Old 05-20-2014, 02:11 PM
BenzWorld Member
 
Date registered: Apr 2014
Vehicle: 1982 300CD
Location: So. California
Posts: 50
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Quote:
Originally Posted by cargirl View Post
Would it make sense to buy the head and the cable before I remove the instrument cluster so I can fix the problem right then and there. And what about the odometer - I am not sure if that is needed to pass inspection but I would like to have it fixed.
The odometer is a relatively easy fix but I would need a picture of the back of your speedometer head to explain it to you. If the MPH needle is not moving, and the speedo cable is not broken, you will need to send your speedometer head to a speedometer shop for repair. As long as you have the oil pressure gauge hooked up and the large bundle of wires plugged in to the back of this same gauge, you can drive the car day or night without the rest of the instruments. You will not have a glow plug light during this time, but as long as you wait about 15 seconds before starting the car there will not be a problem. I currently own a 1982 CD, a 1985 300D, and a 1983 300TD and over the years have owned a dozen or more of the Mercedes W123 cars.
BWhitmore is offline  
Sponsored Links
Advertisement
 
Reply

  Mercedes-Benz Forum > General Mercedes-Benz Forums > For Sale/Wanted/Trade/Giveaway

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
     
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode



    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On

     

    Title goes here

    close
    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome