cruise control problem

[werminghausen]

Cruise control of my SDL works in general but it is sketchy in times and does odd things.
problems are: It disengages on bumpy roads.. This happens regularly. But then once in a while it doesn't do what it's supposed to do..it has once accelerated whithout warning or signal... but this happend only twice.

So the question is: Is teh culprit one of the 3 parts (stalk, amplifier or actuator) or is it a combination? What do you think?
Martin

[Marvelicious]

As I understand it, its usually the amplifier. Heres a diy link and a link to an outfit that rebuilds them. Mine has a few weird problems as well, but it has gotten better with use if you can believe that. Read the rebuild outfit's policy on cores before you attack your board with a soldering iron though.

http://www.mindspring.com/~houlihan/merc/cruise.htm

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

[shertex]

Needs to be properly diagnosed. Either send both amp and actuator to GDL for evaluation or pay an hour's labor to the Mercedes dealer for a cruise diagnostic. While it is true that it's often only the amp that's the problem, it's also true that sometimes a bad actuator can cause the amp to go bad....in which case only rebuilding the amp is a waste of money.

Cheap first step: call Peter at GDL and explain your symptoms. He's very friendly and helpful.

[werminghausen]

It is obvious that my cruise is working but if engaged it stops working by itself. The most obvious cause might be a bumpy road or sometimes it is unclear what makes it stop.
I contacted the person who is doing the reman and he says I should change the stalk and go from there.
What is your recommendation? Would you replace the stalk?
I also got an offer for rebuilding the amplifier for $120 from someone who has done my Pushbutton unit for the hvac in the car (was also just 1/2 price compared to Programma)

Actuator: what goes wrong with it? What are the parts that need replacement?
Is this a DIY job?
Thanks, Martin

[toomany MBZ]

I don't think the stalk is your issue, I'm betting the amp.

[Marvelicious]

Bumpy road, I can see how that COULD be it. I'd be inclined to at least take the stalk apart and look it over before I started throwing money at parts.

[toomany MBZ]

You need to remove the steering wheel to get to the stalk (combination switch).

[scottmcphee]

I'm betting actuator.

The amp has an inclination to "let go" of cruise when digital or analog conditions aren't right.

If the feedback potentiometer in the actuator is sketchy (drops signal, skips across dead spots, etc), or the actuator motor drive is not getting the lever to its intended position, the the amp reads these things as "not right" and drops cruise.

Lube up the mechanisms on the actuator first, see if something is binding. That would be the first step, especially if a "bumpy road" is causing the drop.

Of course the amp itself can have a poor solder joint or connection pin. Which over a bump would cause same thing, so it could be amp. Or for that matter, connector at the actuator. Ensure the actuator connector is not loose / frayed / dirty / etc.

[werminghausen]

Originally Posted by scottmcphee

I'm betting actuator.

The amp has an inclination to "let go" of cruise when digital or analog conditions aren't right.

If the feedback potentiometer in the actuator is sketchy (drops signal, skips across dead spots, etc), or the actuator motor drive is not getting the lever to its intended position, the the amp reads these things as "not right" and drops cruise.

Lube up the mechanisms on the actuator first, see if something is binding. That would be the first step, especially if a "bumpy road" is causing the drop.

Of course the amp itself can have a poor solder joint or connection pin. Which over a bump would cause same thing, so it could be amp. Or for that matter, connector at the actuator. Ensure the actuator connector is not loose / frayed / dirty / etc.

All good suggestions. I can check 1) if the stalk plug is connected (well...removing the steering wheel only...I hope) 2) I can check the actuator- take it out and inspect (not sure if I need to take the intake off for that...hopefully not and 3) amplifier reman..which costs some money.
I 'll check 1) and will do 2) and then see what happens.

[werminghausen]

update:
I had my amplifier remanufactured ( I know a good address/nice person who can reman the unit for less than the other companies) , also I changed the
stalk. It seem to work now properly.
So the problem was not the actuator!

Martin

[shertex]

Originally Posted by werminghausen

update:
I had my amplifier remanufactured ( I know a good address/nice person who can reman the unit for less than the other companies) , also I changed the
stalk. It seem to work now properly.
So the problem was not the actuator!

Martin

Glad things are working well. However, an actuator problem is not necessarily ruled out in that you don't yet know whether the original amp failure was caused by the actuator....but time will tell. (Although you could ask the guy who did the rebuild whether he noticed any damage to the output transistors.) In my case, my rebuilt amp lasted for three weeks or so and then died. Subsequent research verified that the actuator was the problem. The longer you go without a problem, the more confident you can be the your actuator is OK.

Not trying to rain on your parade....just trying to help people learn (and save money) from my mistakes.