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Old 12-08-2012, 03:27 PM   #1 (permalink)
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Thinking of getting the cruise control working. Where do I start?

1984 300CD

I realize that cruise control rarely works on these. Mine is no exception. Since it hasn't worked in the year that I have had the car, I don't even know where to start. What should I check first? Are there any good write ups on how these even work?
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Old 12-08-2012, 03:39 PM   #2 (permalink)
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W123 E,CE,D,CD,TD,TE Class - Benzworld.org - Mercedes-Benz Discussion Forum

...might be something in the diy section
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Old 12-09-2012, 09:35 AM   #3 (permalink)
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Quote:
Originally Posted by gregp1962 View Post
1984 300CD

I realize that cruise control rarely works on these. Mine is no exception. Since it hasn't worked in the year that I have had the car, I don't even know where to start. What should I check first? Are there any good write ups on how these even work?
I had my cruise amp replaced earlier this year. the cruise will engage, but it won't accelerate on a hill, and won't really hold the speed. I'd save your money/time for another repair. I'm about to take mine out...
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Old 12-09-2012, 09:52 AM   #4 (permalink)
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...a lot of people have been successful by removing the amp under the dash (?) an re soldering the connections. the solder they used cracked over time. i think its non reson soldier you want but youd have to check to be sure.
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Old 12-09-2012, 11:09 AM   #5 (permalink)
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My cruise control is broken and since I only use it on very long drives, maybe once a year or so, I just disconnected it and plan on removing it at some point.
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Old 12-09-2012, 03:13 PM   #6 (permalink)
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I too would like to get mine working and have searched but too no success...although my cruise control does work if you count heavy acceleration as working, works great for fast passes-55 to 80 in like 1 sec, deceleration only seems to work if you hold it, then its back to heavy acceleration

Any thoughts?
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Old 12-10-2012, 08:26 AM   #7 (permalink)
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I have a 1984 300CD as well. I have repaired the cruise on mine. There are four main components to the system with wire in-between them all.

1. Amplifier
2. Servo motor
3. Control switch
4. Speed signal generator

I first checked the servo motor, which pulls on the throttle linkage, as best that I could. The electric motor ran well and the feedback wiper was in good shape and the gear train was in good shape so I figured it as OK. I then checked all the functions of the Control switch electrically and it was good. Next, I checked the speed signal generator which looked OK. That left the amplifier as the most probable culprit. I decided to purchase a remanufactured unit, done by Programma. I my case the amp was the problem! I used an electrical multi-meter and troubleshooting information from a website GDL-online.com: Test Procedures - Table of Contents. They offer troubleshooting documents and remanufactured servos and amps along with many other products. If you are not comfortable using a multi-meter and working on electro-mechanical devices a DIY repair may not be the best choice! I would guess that the amp is the most common point of failure.
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Old 12-10-2012, 06:02 PM   #8 (permalink)
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+1

Everything looked OK on mine, but it didn't work at all. I got a rebuilt amplifier from Ebay 4 years ago, and it's been working perfect ever since.
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Last edited by theo3000; 12-10-2012 at 06:05 PM.
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Old 12-10-2012, 07:14 PM   #9 (permalink)
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https://sites.google.com/site/mbcrui...me/diagnostics
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