My wheels were not the issue, as they were installed at the MB Dealership. Although the wheels are larger in size, the tires are low profiles. Anyways ... here is the answer I received from the other site and this was the real issue:
There are only 3 parts that operate the cruise control, the switch at the steering wheel, the engine control module & the idle speed controller\cruise control actuator are one part!! since the you can advance the speed i would say that the steering wheel switch & the engine control module are in good working condition, i would suspect that the idle speed controller\cruise control actuator is the problem. this actuator is a common problem with this model\engine. I would have thought by now with this engines age\mileage that this part should have been replaced already, back when these cars were around the c\c actuator wire insulation would come apart letting bare wires touch each other. looking at these wires is something you can do yourself. the cruise control actuator sits under the intake manifold, has big thick black wire harness coming out of c\c actuator. let me know if you are interested in continuing with further diagnosis??? these c\c actuator were expensive but you can by rebuilt units. the proper way to troubleshoot would be to hook MB scan tool to car & run test on c\c actuator!! you may want spend a little money trouble shooting?? changing parts & guessing gets expensive!! I would love to help let me know what you would like to do from hear!! parts prices, disassemble?? let me know how i can help!! PS i drive a C class with 234k on it, love it, good luck!! one last thing check all the rear brake lights if brake light are out , c\c inop!!
mbfixer-- Mercedes Technician --
Apr 22, 2009 at 9:09 AM
