The crusie control is inop on my '87 560SL. Mostly it doesn't respond at all, however,it did engeage one time, but was extremely erratic (speed up/slow down). Any ideas which unit is bad, or how to troubleshoot the system?

This system has 4 major components and each one should be tested independently of each other.
1. Actuator
2. Stalk switch
3. Speed sensor(built into the speedo)
4. Control unit (Replace if all others
check out OK)

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM