Hello everyone.. My 1985 w126 300sd has an interesting and often quite-frustrating issue: new cruise control amplifier (http://www.adsitco.com/) recently installed, which remedied the completely non-operational cruise control system. I'm extremely pleased with the accuracy which this system maintains speed (+- 0.5mph verified by GPS) but once my speed exceeds approximately 70 mph the cruise fails intermittently. Very rarely does this occur on flat pavement; usually right at the bottom of a hill as I start to climb. The cruise control ALWAYS comes back on-line with a quick flick of the 'resume' on stalk but repeatedly cuts out (sometimes within 2 seconds, sometimes more than 30 sec) while climbing the hill. Never cuts out downhill, flat ground, or at less than 68-70mph.

I've verified proper operation (using cruise control testing procedure found here on MBshop.com) of cruise stalk, cruise actuator (operates smoothly with no rattling, grinding, internal gears in good shape and nicely lubricated and hold-in solenoid actuates effectively), speed sensor operation (measuring voltage, not with o-scope, up to approximately 45-50mph while on-jack stands in driveway) amplifier wiring/voltage, grounds, Osram taillights, linkage adjustment.... I'm not sure what to suspect: speed sensor is supposed to be pretty reliable and actuator seems to check out okay...I just hate to go spending mucho dinero for a new 'fill-in-the-blank(potentially broken part)' if it's not needed.

Has anyone else experienced symptoms I've described? Has anyone arrived at a resolution? Please forward any and all info you may have.

thanks very much in advance,
Erik d.

__________________
Erik deVries
ASE Certified
Automation Engineer
1985 Mercedes 300SD 375,xxx miles, Euro-headlamps, Bosch HID, Boston/Alpine audio
1982 Mercedes 300D 358,000 miles Boston audio, FOR SALE
1997 Dodge 2500 4x4 long bed ext cab Cummins 5.9L, BFAF, ATS trans, billet converter, #0 torque plate full-forward, star wheel full forward, (~295HP & ~680lb/ft G-tech), 5-inch turbo-back exhaust, VIAIR on-board air, LOUD Nathan K5 TRAIN HORNS , 35-inch; BFG Mud Terrain, 2006 Ram 2500 17-inch Aluminum wheels.