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Mercedes 300 SD, 1985
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10 Posts
Discussion Starter #1
Hi,

My cruise control does not hold. It will speed up when holding the lever, but does not hold the desired speed. Specific reason for doing this? Amplifier?, actuator?:confused:

thanks
 

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1993 300TE, 1995 E320 Wagon
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1,895 Posts
It's almost always the amplifier, found under the dash above the brake pedal. Finding a working one is sometimes problematic (they are relatively common at scrapyards, but I can't test one out, as I have the wrong type of car, and they are often model- and year-specific, I've found).

There are several threads on trying to resolder "cold joints" inside the amplifier, but these repairs are not always successful. I've also seen a repair of the 12-pin connector, but again, this may not be the issue.

So you can see that you're going to have to try several approaches. Best bet for a DIY would be to get a couple from a junkyard (they range in cost from about $10 to $25, depending on the yard), and my experience is that about one in five or so work. But you'd at least have a couple to compare yours to. You can also buy a rebuilt unit from a guy in Morro Bay, CA-- I forget the company name though-- it is in one or two threads here though. I think he charges about $200, maybe $250.
 

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1990 560SEL
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61 Posts
Resoldering

I had the exact same problem on my '90 560 SEL. The cruise would take, then surge a few times before disengaging. After a while it stopped working altogether. You can get remanufactured cruise control ampliphiers from a few sources, and for a few hundred dollars, but I found that resoldering the circuit board in the ampliphier did the trick and cost nothing. There have posts before about the procedure.
 
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