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#1
06-07-2010, 04:54 AM
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Cruise control amplifier..
I was reading in another post somewhere on here and someone mentioned repairing a cruise control amplifier. I have an 83 300d turbo,the cruise quit working so I changed the switch out with an extra I had laying around. It worked fine for a little while and quit again. I talked to a mechanic who is pretty knowledgeable on M/B. He said that if the switch was funtioning and things were working normally then it was probably the c/c amplifier.Before changing the switch it would work intermittently and at times would engage and accelerate on its own. So do you gurus think I have a bad c/c amplifier or some other gremlin? Also can anyone tell/give me a link to the amplifier repair procedure,I seem to remember some soldering being discussed. Someone also mentioned that once you solder them they will no longer be accepted for cores or rebuilders (not too concerned with that). Thanks for any help/replies,Chuck.
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#2
06-07-2010, 08:33 AM
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I'll agree with your mechanic, the amp is usually the problem. A cold solder, I would think. To correct that, you need to open the amp and inspect, if you find any, re-low the solder or even add a bit.
I also understand if you try to fix it, the repair shops that do this won't touch it.
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83 SD 84 CD
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#3
06-07-2010, 12:42 PM
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The amp is not just the issue. There is a device (actuator) right above the pwr steering where the accel linkage is connected to that is part of the cruise that goes bad. Below is a link of a place to send that part to. I remember speaking with that person who I found very knowledgeable with the 300d CC.
Here's the site: http://www.gdl-online.com/begin.html
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the sooner you start... the sooner you'll get done  If it ain't broke, don't fix it.. Its always simpler to tell the truth... 2007 Honda Accord EX 2007 Honda Accord SE V6 96 C220 97 Explorer - Found Another Home 2000 Honda Accord V6 - Found Another Home 85 300D - Found Another Home 84 300D - Found Another Home 80 300TD - Found Another Home Previous cars: 96 Caravan 87 Camry 84 Cressida 82 Vanagon 80 Fiesta 78 Nova Ford Cortina Opel Kadet 68 Kombi Contessa Last edited by tobybul; 06-09-2010 at 09:36 AM.
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#4
06-07-2010, 01:34 PM
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Fortunately for the OP, the cruise actuator in the W123 diesel is out in plain sight, easy to get at and remove. The actuator is a mechanical device, fairly easy to open up and repair. Often it's a position sensor (variable resistor) that has gotten dirty from years of service, or simple binding due to grease that has aged and turned into amber. Someone (DieselGiant?) had a post that showed this operation.
The cruise switch seems to be reliable unless it gets damaged in a dash-removal or similar project. I've never had to work on one. From personal experience and years of reading threads on this forum, it's almost always (80%?) one or more cold solder joints in the amplifier board. Sometimes you can actually see the cracks in the solder joint. To be safe, resolder everything. Be patient, there are a lot of connections. The two boards that I worked on several years ago are still working. Jeremy
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 "Buster" in the '95 Our all-Diesel family 1996 E300D (W210) . .343,000 miles Wife's car 2005 E320 CDI . . 148,000 miles My car Santa Rosa population 177,300 (2026 projected) Total. . . . . . . . . . . . 668,300 "Oh lord won't you buy me a Mercedes Benz." -- Janis Joplin, October 1, 1970
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#5
06-07-2010, 01:45 PM
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Can anyone offer a quick guide on how the re-soldering should be done? I've never used a soldering iron before but have access to one. (Should I not, given such inexeperience, take this on?) Thanks.
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05 E320 CDI - 185K miles 82 300D - 200K miles (sold)
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#6
06-07-2010, 01:57 PM
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On something that small, an experienced hand is the way to go, but practice. The biggest issue is not over heating the soldered pins, as you may destroy whatever is on the other side.
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83 SD 84 CD
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#7
06-07-2010, 02:04 PM
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Quote:
Ive done a couple of these, also replaced the 'memory' components that had become faulty causing a slow drop in speed over time.... --There seem to be two types of actuator, a Vacuum diaphragm type, mounted on wheel-house and connected by a bowden cable to the throttle-linkage and the other type which has a motor, gearbox and position-sensor. --They both work in a similar way, and the controller (Amp) suffers from the same ailments.... 
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http://i190.photobucket.com/albums/z...0TDnoplate.jpg Alastair AKA H.C.II South Wales, U.K. based member W123, 1985 300TD Wagon, 256K, -Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.  W114, 1975 280E Custard Yellow, -Great above decks needs chassis welding--Really will do it this year....
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#8
06-07-2010, 02:35 PM
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Where is the CC amp located? And is it pretty simple to remove?
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the sooner you start... the sooner you'll get done If it ain't broke, don't fix it.. Its always simpler to tell the truth...2007 Honda Accord EX 2007 Honda Accord SE V6 96 C220 97 Explorer - Found Another Home 2000 Honda Accord V6 - Found Another Home 85 300D - Found Another Home 84 300D - Found Another Home 80 300TD - Found Another Home Previous cars: 96 Caravan 87 Camry 84 Cressida 82 Vanagon 80 Fiesta 78 Nova Ford Cortina Opel Kadet 68 Kombi Contessa
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#9
06-07-2010, 02:45 PM
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On my 82, it is up under the dash, above the pedals on the driver's side. I wouldn't say it's "simple" to remove, given the gymnastics necessary to get to it, but not bad.
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05 E320 CDI - 185K miles 82 300D - 200K miles (sold)
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#10
06-07-2010, 03:09 PM
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On my Euro (UK) 1985 300TD its behind the kick-panel at the side, in front of the door, accessed by removing the trim...
It appears, that on US cars, its mounted on the Brake-Pedal bracket....
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http://i190.photobucket.com/albums/z...0TDnoplate.jpg Alastair AKA H.C.II South Wales, U.K. based member W123, 1985 300TD Wagon, 256K, -Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog. W114, 1975 280E Custard Yellow, -Great above decks needs chassis welding--Really will do it this year....
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#11
06-09-2010, 09:15 AM
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The contact below repairs them and exchanges your old amp. We had ours done about 15-20 years ago, no problems since. Well worth the cost and this person knows what he is doing.
Jim W. George Murphy MBCA Technical Director [email protected] 865-482-9175 Voice or FAX
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