PeachParts Mercedes-Benz Forum - View Single Post - Cruise Control Amplifier Diagnostics & Amplifier Repair

JamesDean · #37 06-08-2026, 06:10 PM

Generally speaking, capacitors are only part of the problem. Solder joints, the big resistors, some transistors, and finally logic gates can all be part of a non-working vacuum unit.

Whenever a unit comes in I replace the capacitors regardless if they measure bad or not as the parts cost is less than $5 total. They are pushing 30+ often 40+ years of service and are effectively at the end of life. Sometimes they present with obvious visual problems like venting or literally coming apart sometimes they look fine.

Its quite possible your unit has some bad solder joints. Often times I wont see them upon an initial visual inspection but as I work through the unit I'll spot them. Sometimes they are truly horrible and noticeable from a distance.

If you want to continue your investigation I'd suggest solder joints next. With those capacitance values, I'd expect to see some signs of life out of the unit. If its doing strange things I might suggest solder joints next. Loss of speed (assuming the vacuum system is solid) would point at he 0.1uF capacitor.

Alternatively, if you would like I'd be happy to take a look at the unit for you or maybe easier, dig one up from my core pile and repair it for you.

--Kris