Intermitant Cruise Control W202 C230 - PeachParts Mercedes-Benz Forum

N41EF · #1 09-24-2007, 08:35 PM

Ok, when I bought the car the stalk for the cruise control was broken, like a wet noodle stuck in the colum, wiggled it and had no real action. Replaced switch and test drove in the neighborhood and cruise worked great, much back patting, I CAN FIX ANYTHING. The, on the interstate, cruise doesn't work at all. Seems at less than 45mph it works great, several miles, no issues. At 55 MPH it will work for a short period, sometimes 10 seconds, sometimes a minute, never very long. At 65mph or above you can feel it engage and immediately drop out. Thought it might be a dirty contact, worked the cruise switch, the brake light switch, no change. Seems the faster you drive the shorter time it works, and won't really engage at all above 65mph. Where does the W202 get the car speed? Is there a speed sensor somewhere? Any other usual suspects to check. I tried watching the brake light and say nothing, but could still be a brake light switch. Any Ideas? Thanks guys! Chuck

mbdoc · #2 09-25-2007, 10:03 AM

How about the tires? are they all the same size? If they vary by more than 3/8" in circumference the traction system will kick the cruise out at higher speeds!

N41EF · #3 09-25-2007, 08:58 PM

Good guess, but I just put 4 new tires on it. How does it measure speed? My W123 had a sensor on the back of the speedometer, but this cluster is all electric. Thanks.

Arthur Dalton · #4 09-25-2007, 11:22 PM

Speed sensors on all 4 wheels..if the CC module sees a difference out of allowable tol. spec,. it will kick out the CC.
The faster the wheels spin [ higher MPH], the more sensitive the difference becomes. [which is why you noticed the problrm increases w/speed]
If all tires are the same , you want to check that the PSI of each is Identical.

Will_w202 · #5 09-26-2007, 12:24 AM

Mine did this above 60 with the OEM Continental tires. Brand new, one was out-of-round. Did it start when you put the new tires on?

N41EF · #6 09-26-2007, 09:36 AM

Switch was broke when I bought it, put tires on it before I replaced the switch. Is there a way to see which wheel sensor is kicking it out? I don't have an ABS light, and no fault codes. I have the front tires I think 4 pounds lower as the sticker says, will try inflating them to same pressure and see if that changes things.

mbdoc · #7 09-26-2007, 10:25 AM

JUst use a string OR tape measure on the circumference of all 4 tires....move the "taller" tires to the rear! IF that is the problem IT will go away!

Arthur Dalton · #8 09-26-2007, 11:42 AM

A trick I use is to take a Q-tip and break off the cotton swab end, making a small ball. I then dip it in white paint [ or any type marker liquid] and stick one in each tires thread. Then I drive the car on a blacktop drive a little over one tire revolution.
You now have 4 sets of distance marks on the driveway. They should all match closely. The advantage to doing it this way is you get the actual rolling circumference of the loaded tire on that car.
This is also a good trick when doing calculations for speedo and gear changes.
Usually one will find that problem to be a simple difference of tire PSI..
[ which changes the rolling circumference]

N41EF · #9 09-29-2007, 12:26 PM

You guys nailed it! The left front tire was bad, not sure if it had a bubble, or was mislabeled or what, but three tires measures about 197cm, and the left front was 202cm. Had just bought the tires, the store put it on a lift, measured all four, and replaced the oddball with another new tire. Thanks to all who helped out, I'm sure I'll be back with more questions. Chuck

Arthur Dalton · #10 09-29-2007, 01:06 PM

Thanks for the confirm reply...
Many times we get dis-belief when we mention the first step on these complaints is tire sizing/PSI...
No B/S..... once you know how a wheel sensor works, it is just common sense that wheel circumference is a MAJOR Factor.