W124 300D Cruise Control
 

My cruise control will accelerate and set using the control stick but it won't do it for very long.

So far, the maximum is about ten seconds.

I then try again and it engages/accelerates for about the same amount of time before it cuts out.

What could be the problem?

There may be one or more cold solder joints in the pc board of the amplifier under the dash, driver's side. Many threads here on removing to replace with a rebuilt or resolder the board yourself if you have that skill. Warning: the people who sell rebuilt amplifiers want your bad one as a core and will not accept one that has been resoldered. So, you have to make up your mind which way you want to go, before you plug in the soldering iron. A rebuilt amplifier is $200-300, I think.

Also keep in mind that sometimes the amp goes bad because the actuator has gone bad (draws too much current). So you could repair/replace the amp only to have it go bad again. This was my experience on my 92.

Go look on gdl-online.com and read their diagnoses instructions. You have to make sure the actuator isn’t drawing too many amps before replacing the old amplifier (or it will short it out).

I tried soldering my board which didn’t fix it so I got a rebuild one from the benz store for about $160. He didn’t care (or even look to see) that I had cracked open the old amp.

It sounds hopeful that you at least have some signs of life of working cruise so Im betting its just a bad amp.

You can also go aftermarket.

antique style web site, but so are our cars! You may find the site works better with Internet Explorer, cut to the chase a bit and launch this page:

http://gdl-online.com/begin1.html#contents


great diag's

There is a good thread about going aftermarket for the cruise control. Audiovox CCS-100 works well. I found one for about $100 bucks. You have to search around. Here's the thread: http://www.peachparts.com/shopforum/diesel-discussion/219993-official-audiovox-ccs-100-install-thread.html?highlight=audiovox+ccs-100

I'm handy and I've got a couple complete spares of cruise modules, activators, switches, etc... so I'll go through the diag's and fix it myself.

My cruise symptom is, it cuts out after a few seconds of normal operation.. much like the OP of this thread.

I'll let people know what solved the issue in my case, when I figure it out.