MB 350SDL Cruise control

I would start out by changing your brake pedal switch... it is for both the brake light and cruise control... together.

Where is it located exactly? Thank you! karl

Just above the brake pedal... just press the brake pedal and you will see the switch "opens" up... You do have to remove the underdash cover to see it.

Even before taking anything apart, I'd have someone check the brake lights while you step on the pedal. As was pointed out, the same switch works both, so it's possible your brake lights aren't working either, which is dangerous.

It is usually the cruise control amplifier that goes bad... it is also by the switch you just pulled out. The fact that stepping on brake didn't shut off the cruise control makes me suspect the brake switch. It may look okay... but if the switch is cheap... you can see if it helps with a new one.

If you are very electrical savvy... you would clean all the contacts.

I'd locate the wire from the brake light switch where it shows up on the connector to the cruise control electronic module. Verify that you are getting 12V and 0V with a test light while operating the brake pedal. If you are, then try reseating the connector. After that, it sounds like the module is kaput. You can get remanufactured ones for about $200

The switch has been tested , and work properly. Brake light is working OK. What will be the next to check out? Karl

How did you test it? Simply pressing the brake pedal a couple of times and having your wife tell you if the brake lights are on is not valid. I had a similar issue to yours and it turned out that the brake lights failed to come on about one out of 10 times, and even then it was not consistent.

Josh

I took the switch out , and used a Multi meter and cycled it several times. To get to it , I had to take out the cruise control amplifier , and that meant taking out the plug for both things . This has probably solve a bad connection, by re-plugging it. karl