cruise control - PeachParts Mercedes-Benz Forum

Jassper · #1 09-14-2003, 04:25 PM

Hello everyone,

I know this won't be of any specific help but I'll write down all I found about my cruise control. As a matter of fact I found nothing.
But first things first.

My cruise control acted weird. It had so in the past few years. It would work fine but every now and then it would not engage. Of course one doesn't use CC all the time to tell whether it works or not. Approximately twice in 6 months it would not engage no matter what I did. I started the car, got on my way, pulled the lever up and nothing. A few turn on/offs with ignition have always helped. After that CC would work until it refused to engage again after a few months. Alas, every time I wanted to have a look at it it worked. It was hardly a cause to spend the effort and time. So a few years went by.

A week ago CC gave up on me again. This time, however, no ignition on/off helped. Time overnight was of no help either, the CC would not engage. Although there was no need for CC in the city you can imagine how frustrated I was just knowing CC did not work. Then, all of a sudden CC engaged when driving. About half an hour after I pulled the lever up. It began to speed up, I had to cut it out at 60 mph as there was traffic ahead. Could this be a sign of CC making up its mind and healing itself? No. I was unable to engage it ever since then. That was a week ago. Today I tried to engage it, it worked for a few seconds, then gave up.

Fed up with this all I decided to take the components apart. I removed the amplifier first. Easy to take apart. I resoldered the connectors but don't think that was the cause of the trouble. The amplifier is a single circutry board with a few components on it. All dipped in flux before assembly (must be sensitive to humidity), the board was manufactured and designed cleanly, looked tidy, not even a hint of smell from something burnt. I reassembled the amplifier and put it back. There is a removable relay at the back of the amplifier. Could this be the faulty part? Maybe. There is no way to test it for me. It looked good as new though.

My next (and last) step was to have a look at the actuator in the engine compartment. It can be removed easily, 4 accessible screws only. I took it apart - also the interior looked clean. Inside there was a relay that engaged the gearbox made of 2 plastic gears (sprocket wheels) and a board with 2 carbon tracks to measure position (resistance) of one of the wheels. I cleaned the tracks and resoldered the power cables just to make sure I did everything I could while it was out. I should note the lid (apart from 4 screws) is also fixed with one rivet which I had to remove. On the bottom of the actuator is an electric motor, fixed by 3 screws and a rivet. I removed the screws and the rivet but when trying to pull down the motor I felt resistance, as if I pulled a spring. In the end I did not remove the motor, put the screws back on and the actuator back on to the engine block.

I did a test drive at no avail - CC did not work. Then, a few hours later it began to work again. It worked until the end of to-day.

I am confused. There must be either a cold solder point I had overlooked, or the relay is bad or the Hall sensor is. Or an electric component on the amplifier board fluctuates with temperature. I did not take apart the Hall sensor, I had it out once and one cannot see anything peculiar on it. I am afraid should the CC fail to work (which it will, because an older Mercedes is a car unhappy to be in full working order, once you fix one thing another starts showing up) I will have to find spare parts and change them one after another to locate the culprit. If only I find a yard with a close-enough type of Mercedes and an owner willing to either loan me those parts or buy them back, even with some loss to me, because buying all of those parts at once would be costly.

Wes Bender · #2 09-14-2003, 06:31 PM

If you do a search, you'll find a ton of stuff on CCs. Maybe you've already done that.

In addition to what you've already done, I would also check, clean and tighten all of the pins and sockets in the plugs in the CC system.

Good luck with it.

Wes

ck42 · #3 09-15-2003, 10:26 AM

Here's all my info on CC stuff. Hope something here will help you or anybody else having issues.

1) Decent writeup on troubleshooting

Here's another one on just looking at the Amp...not much good info but pretty pictures

These last 3 are w/o a doubt the most useful. Spend most of your time looking at these. There are several OTHER articles regarding troubleshooting that I did NOT list but can be found on the site...just look around.

LINK PAGE for several excellent articles....take your pick.

PAGE to pick your year actuator for troubleshooting.

And finally, a great guide in how to TEST your actuator...based on a chosen year for example.

If you can't find the problem or at least get close after looking through those last 3....then I don't know what to tell you.