Cruise Control Amplifier Diagnostics & Amplifier Repair - Page 3 - PeachParts Mercedes-Benz Forum

JamesDean · #31 04-02-2022, 02:46 AM

Hey hschickel,

Still alive!

You can swap in any actuator from 86+.

Electrically they are interchangeable.

Mechanically you just need to swap out the arm and mounting brackets with your old unit.

lsmalley · #32 04-02-2022, 10:54 PM

Quote:

Originally Posted by JamesDean

Hey hschickel,

Still alive!

You can swap in any actuator from 86+.

Electrically they are interchangeable.

Mechanically you just need to swap out the arm and mounting brackets with your old unit.

I was wondering where you were. I just ordered a ton of capacitors and resistors to try to repair my amplifier. I found a good working one from an 88 201. I'm still going to attempt to fix mine though.

JamesDean · #33 04-03-2022, 09:12 PM

Quote:

Originally Posted by lsmalley

I was wondering where you were. I just ordered a ton of capacitors and resistors to try to repair my amplifier. I found a good working one from an 88 201. I'm still going to attempt to fix mine though.

Yeah, I've been around here and there. I've not been on the forums in a while. I do get email notifications still and try to check back soon as I can find the time.

Good luck with the repair! That 88 should have the 005 545 05 32 unit, those are nicer to work on than the older units, far less components.

--Kris

Stefan · #34 06-08-2026, 08:19 AM

Hi,

I'm wondering if there is more to check on this cruise control unit 0015452032 than the two 47MicroF capacitors? They seem to have a relative high ESR of about 5 Ohm.

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The soldering joints actually do not look to bad imho. But can that be delusive?

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Thanks in advance!

/Stefan

JamesDean · #35 06-08-2026, 09:55 AM

Hi Stefan,

There is a 0.1uF capacitor on the bottom left of the board. Its connected to the yellow GUNTHER relay.

That is where the speed reference is stored as a voltage. That one, when it goes bad, will manifest as slow loss of speed over time.

The joints can look fine but when you go through them slowly one-by-one you may notice something you didnt at first glance.

If you can, I'd replace the two 47uFs and the 0.1uF.

--Kris

Stefan · #36 06-08-2026, 01:52 PM

Hi Kris,

thanks a lot for your fast response and sharing your knowledge and expierence.

That 0,1 micro is a foil capacitor, which I would believe shows good mesurement result.

Funny enough that also the other capacitors show good values after having them desoldered.

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From the values point of view: I would not have expected them as suspicious would you?

I guess your expirience shows that they are responsible for the problems although the values show up as OK? So they should be changed in any case?

I have to admit that I cannot recall the fault description from the owner of this unit...

/Stefan

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

Stefan · #38 06-09-2026, 04:01 AM

Hi Kris,

once more thank you very much for supporting! Very much appreciated - especially since you run a business on this. Most managers would not reveal more information due to this but you do

I came accross your webside and saw some very usefull info about how to check the input signals to the unit.

In the meantime I was asking the units owner for describing the behaviour.

So the car is accelerating if you set the cruise stalk but does not store the value - falls down immediately again.

The vacuum has been checked as tight.

So principially I will follow you suggestion and resolder all the joints if you do not tell me different since the fault description is revealed now.

Acctually you said about the 0,1micro Cap:

Code:

There is a 0.1uF capacitor on the bottom left of the board. Its connected to the yellow GUNTHER relay.

That is where the speed reference is stored as a voltage. That one, when it goes bad, will manifest as slow loss of speed over time.

I´m not sure if my mentioned behaviour is a special case of what you said. It (strongly) points into this direction but since the speed is not hold at all it could also point to something else such as a brocken (Günther) relay...?

Looking forward to hear from you and thanks a lot again!

/Stefan