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Old 01-11-2001, 10:51 AM
Posts: n/a
My 83'Turbo 300D cruise control is inop. also my speedometer is inop. but the odometer does function correctly and records distance as accurately as possible for an 18 year old MB. My question is, does an inoperative speedometer disable the cruise control or control any of its functions. Next question is, where and what section of the Mercedes Benz CD service manual tells how to trouble shoot this problem if it even covers the subject. I have not been able to locate it.
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Old 01-11-2001, 11:42 AM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
It's my guess that you have two separate problems. The speed signal for the cruise comes from a sensor that picks up its signal from the rotating magnet in the speedometer. The odometer is gear driven off the same shaft. The only possibility for a common would be if the magnet came off the shaft or the shaft broke. We have them in stock if that is the case. It can we replaced without complete disassembly.

I just checked with my speedo guy and he says they do break the shafts above the spiral drive for the odometer.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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Old 01-11-2001, 12:03 PM
Registered User
Join Date: Apr 2000
Posts: 166
Originally posted by cainja
and records distance as accurately as possible for an 18 year old MB. [/B]
Hey, Jeff,
Don't sell the quality of these instruments short! Mine still works perfectly.

Have a great day.
1979 240D
165,000 miles
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Old 01-11-2001, 12:41 PM
Posts: n/a
300CD Cruise

My brother has a an 84 300CD which had a similar problem . We checked in the shop manual and found a caution statement regarding the cruise comntrol an the brake lights. If these are not MB parts, then you risk damaging the cruise amp. He had non-MB bulbs in his brake lights. We changed them out to MB bulbs and the problem went away.
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Old 01-11-2001, 11:02 PM
Registered User
Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
Cruise Control Diagnostics Online!

Hi there,

There is a site that has some diagnostics that will help you determine the cause of your problem! Here's the URL for it:
They also rebuild the actuators and control units. I don't have any experience with these people, but did make good use of their diagnostic procedure to troubleshoot the cruise control system on my '82. There is also a very good description of the cruise control systems on various M-B vehicles somewhere in their pages. PS - On my car, the actuator motor was worn out. (some armature windings open)

Good Luck!
Richard Wooldridge
'82 300TD/4.3L V6
'77 Jag XJ6
'77 280Z
'74 280C
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Old 01-12-2001, 11:24 PM
Posts: n/a
Cruise Control 83' 300D

Sorry for not answering the replies to my question sooner, but I had to go to St. Augustine, FL to pick up my non-cruise controlled car. I took the advise of the first two replies, because I read them before I left. 1st. I changed out the speedo cable with a used one, and low and behold the speedometer work, but the noise that was generated in the dash was unbearable. I have never heard so much racket in my life, unfortunate the cruise control still was inoperative. 2nd I went by the Pensacola MB dealer and bought 2 new Bosch bulbs for the brake lights and install them. Still no luck with the cruise control.
Now that I have received a 4th reply on how to trouble shoot the cruise control system, that will be this weekends chore. Wish me luck.
Thanks for all the help so far, will let all know the outcome.
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Old 01-31-2001, 09:37 PM
Posts: n/a
Cruise Control 83' 300D

Sorry it took me 2 weeks to post my finding on the CC problem, but here is what I found. I used the test procedures Richard Wooldridge so kindly told me about, you can link on to them at:
It took about 15 minutes studying the print out and locating the componets which where to be tested. The most difficult componet to remove was located on the firewall by the foot brake. After testing as prescribed I decided that repairing the actuator and the amplifier was going to be cost prohibided for a 18 year old car. I need four new tires and lower ball joint more than I need an operation Cruise Control. Thanks to all for your responses.
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Old 01-31-2001, 10:58 PM
Registered User
Join Date: Sep 2000
Posts: 97
Has anyone had any experience with GDL remanufactured amplifiers??
1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)
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Old 02-01-2001, 02:30 PM
Posts: n/a
83' 300D Cruise Control

Not I, I'm too new to this Mercedes form of transportation, I now have a new hobby, its DIY Mercedes. Never knew so many little things needed to be fixed on this car I bought 3 month ago. Am getting great pleasure in fixing them though. Please post if you do buy or use the services of GDL, I like to know for future use.
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Old 02-02-2001, 06:24 PM
Registered User
Join Date: Jan 2001
Posts: 39
Cruise Control Fixes

Cainja seems you and I are simultaneously working on the same problems with our 83 300D's. I've had mine for a month and like you have been fixing the interior lights and cruise control. I'm no expert here but this is worth a shot. If the problem is the amplifier resoldering the printed wiring board or replacing 3 parts worth $3 can probably fix it. I read this on another thread on this site. The parts are available at radio shack and you can do the resoldering.

My cruise control has a different set of problems. It works but it's so herky jerky it could make a sailor seasick. I think it's too much slop in the linkage so I'm going to replace the ball clips next.

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