The VDO Cruise control unit used on the w123, w126, w124 and likely many other mercedes models was also used on a pile of other cars, including Porsche, BMW, even some Rolls Royce I’m told.
They worked good… in 1982. Not so much nowadays, many have died slow deaths, starting out surging and not always engaging, until one day they stopped working entirely.
Let’s change that. I’ve created videos showing the troubleshooting steps for each component. I’ve been working on a document that has detailed instructions, It is not finished. but I’ve attached the current state of it and will continue to update the document as I figure out everything I need to know so I can convey accurate information.
Here is the first video about testing the Actuator under the hood:
Part 2, About testing the control stalk, the power and ground wiring and all the electronics aside from the amplifier:
Part 3, Repairing the cruise control amplifier, Not a difficult task, but rather time consuming.
Here is the link to the current document: