Cruise Control/1987 300E

Recently purchased my 1st M-B, a 1987 300E with 110K. It has a few problems that I wish to address, and it seems that through this wonderful site I should be able to get the correct info. The cruise control basically doesn't work. I've been able to engage it only 2 times, each time it shut itself off within about 15 seconds. Any ideas?? Is this something I could take care of myself? Thanks!!

[JCE]

One of the least expensive checks is to go through all the exterior light bulbs and the 3rd brake light bulb and make sure they are all the same brand and wattage, preferably German bulbs. The speed control switches off when your brakes are applied, and if there is evev a tiny 'strange' ohmage on either brake circuit (each circuit shares a brake bulb with other bulbs - look at the info inside the lid of the fuse box)it can affect cruise control operation. This may not be your problem, but is an easy and dirt cheap possible fix.

Also, there was a recall on throttle linkage bushings. If yours wasn't done that could make your linkage difficult for the unit to control, if I recall correctly.

The system has a controller and an amplifier, and I don't recall the order to check them in or replace them if they have a problem. Check the search feature - this has been discussed a lot over the last couple of years. I am sure some of the techs will answer with even better ideas about what is going on. Good luck, and let us know what you find.

Thanks John! I'll get to work on the light bulb inventory
as soon as I get a free moment. At least it's a place to start.

John- I replaced all of the light bulbs(OSRAM) on the rear of the car. The cruise control now works! Thanks. It was intesting to note that all of the old bulbs looked rather fried......though they all still worked. All of the elements on the inside of the bulbs looked corroded.
I sure appreciate your "quick fix".

I do have another question. Though the cruise now works, and stays on when engaged, it does seem a little bit hesitant when first turned on. Is this a symptom of another ailment or is this how MB cruise controls work? I guess what I'm talking about would be best described as a slight lag when you first engage the CC.

My 1989 was doing the exact same thing. This is my first MB also so I was looking at this grea site for help. My cruise now is rock steady. I fixed it try to fix another problem. All I did was change the Over Voltage Protection Relay and now it works. Not sure if that is your problem but it fixed mines. I'm not even sure what the OVP does to the Cruise control but it worked.