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cruise control issues

Started by RD, 10 February 2022, 03:50 PM


All, my amp was recently rebuilt; I plugged it in & took the car for a test drive. Cruise sets just fine, but the car accelerates an additional 5 mph or so, then goes back down to the set speed. But immediately goes back up for more speed, then back down to the set speed. Does this constantly, even when the Resume or Decel function is used.
Before the rebuild, and before the cruise stopped functioning, this problem didn't occur. Any thoughts?


My rebuild I got from Programa does exactly the same thing, but before my old unit was kaput and did not work at all so I have no baseline. I think it's just the way they are unfortunately.  It constantly hunts to get to the set speed, very annoying and will make you nauseous if you leave it on, so I just don't bother to be honest.  I recall some members saying that after it has warmed up a bit it should stabilize the speed better but for me the sensation is unbearable, much more pressing matters to attend to IMHO 8)
1977 450 SEL 6.9 - Astralsilber


I see!  Thx so much! Maybe I was expecting too much from 70s technology   


Bad news gents, it should not hunt when engaged. Something must be wrong with how your units were rebuilt.

Mine doesn't hunt, but does drift off the set speed over time (slows down). It does indeed get better when CC is enabled for a while.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE


OK thx!  I will experiment more on the weekend, on the freeway at 65+; today I only tested it at 50 mph on the road


The device is designed to hold speed precisely providing everything mechanically and electronically is in good order. It should not hunt nor lose the speed threshold. How do I know that? Mine works that way, but after long hours of checking/repairing the following. Check your vacuum module for leaks. Also the tension of the cable (zero slack). Those can lead to the symptoms you described assuming your amp is ok, and it should as you mentioned is new. Also, there's a sensor just behind the speedometer. It needs to be well fixed and clean. Every pin in the connector to the amp needs to be clean and free of corrosion. Typically, this area can take water if there are/were leaks from the firewall (a common/known issue) dripping through the parking break mechanism, fusebox, windshield, airbox plugs, rubber plug for vacuum lines, etc, etc, etc... the list can be long.
Good luck
W116 1977 280SEL & 1979 280SE
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So the first unit I had as a rebuild was apparently not done right; the 2nd one I bought was rebuilt by Programa; no issues with it!