A few days ago I was about three hours (200 miles) into a trip. Some on two lane country roads, but most on interstate. Cruise was on for almost all of the trip. At the end of about 15 miles of country road, I stopped at a stop sign. When I continued I hit resume for the cruise. It did not activate and got message "Cruise Control Inoperative." Tried to reset, but wouldn't. Stopped about 4 miles down road at a store and turned off the car. Started back up and cruise was fine. On 250 mile return trip over same roads, no problems with cruise.
I use cruise a lot when I am going to be travelling a consistent speed for several miles or more. Better gas mileage and way fewer speeding tickets.
Any ideas as to what may have triggered inoperability of cruise?
BTW, driving about 5 MPH over posted limits, I got 30 MPG going downstate and 28 coming back.

 

Did you get a "time for a break" warning? I think it disables the cruise until you stop for a donut and cup of joe. You must have been driving erratically.

 

BINGO. I'd bet a dollar to a hole in a donut that this was the "problem".

 

Wow, really didn't know about the "time for a break" warning, LOL.

Seriuosly though, were you in Sport mode? I hated the CC not working when in Sport on the C63 I rented this spring. My CL doesn't care what mode it is in, CC always works.

 

I've had this happen on my wife's 2007 R350. If I restart the car it kicks back on. Seems like a software glitch as it usually happens as I re-engage the cruise after having turned it off.

 

I guess you didn't read the whole thread...

 

No Coffee Cup warning or anything. I had given a turn signal, stopped to turn, speeded back up and then tried to resume cruise.
Actually I did get a Coffee Cup/Time for a break? warning on the trip back, but it did not cancel the cruise. And I drove for at least an half hour after that in cruise.
Don't think I was driving erratically, but was probably not staying in a straight line in my lane. At least not nearly as erratically as when I was avoiding truck tire carcasses, dropped lumber, etc. in the road.

 

My car two days ago just had all these warnings:

Airbag, blind side assist, lane assist, anything that was electronic including COMMAND and AC was off/inoperable. All the dashboard warning lights were on like a rainbow. It went away after waiting for 5 mins

The front of the car fan starting going at its highest speed and it was so loud and wont stop scared me. I took it in to the dealership yesterday. Today they told me it might've been a relay issue and a software issue and still not sure.... My check engine light was on and yea.. Still waiting on the results...

 

I'm trying to think back (my Bluetec was totaled in January)...I had Distronic and got the coffee cup warning many times on long trips.Sometimes the warning was legit (I was drowsy) and other times it was absolutely unfounded.However,I don't recall the cruise control ever having disengaged with the coffee cup warning.All I had to do was press the "OK" button and all was well.However my cruise control did become inoperative (along with the other features of Distronic) on a number of occasions...all but a couple being connected to serious snow/slush/ice on the car.And the other few times were connected,I believe,to extreme cold (-25F).

 

It is unlikely the extreme cold (-25F) is an issue in the past few weeks :p :

 

True enough.I was just reviewing the occasions when my cruise control failed.

 

There was also a great roaring noise from the fan-irrespective of engine speed. The dealer finally concluded that it was a problem with a relay that controlled the fan. They also speculated that dealers configure cars that are loaned or used for demos to create just this condition if the car is not returned within the time deadline specified.

 

I have had failures of the Distronic, Lane Assist, etc during periods of rain, driving mist, fog, etc. Knocks off (inoperable) for about 5 minutes then restores itself.