Date registered: Aug 2002
Vehicle: '85 2.3-16 '99 C280 '11 GLK350
Location: Scottsdale, Arizona, USA
Mentioned: 0 Post(s)
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From that period, the usual culprit is the amplifier circuit board having broken cold solder joints. The fix is simple yet tedious . . . opening up the case and reheating all the solder points with a low watt iron to renew the joints.
The other culprit is the electrical servo, connected to the throttle assembly under the intake that adjusts the throttle speed.
Also, make sure that your speedometer cable hasn't stretched or is binding, that can also disable the cruise system. A stretched cable tends to be "bouncy" at low, under 10 mph, speeds.
Don't fall for the "non-OEM" brake light bulbs with the out of spec resistance value, that's been debunked long ago.