Has anyone had any experience with their cruise control working, as in it holds the correct speed and everything, except it surges? It's like the throttle inputs are not very smooth. It has done this with the 2 different actuators I have tried.

Could it just be the amp giving up? I wanted to get your opinon before I cracked it open to try to repair it.

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1998 E320 Wagon

1992 300D 2.5 TURBO

1991 560SEL M119.960

1986 300SDL TURBO

1992 500SL Parts Car

1991 420SEL Parts Car

Yes. When that happened to me the cause was a bad amp.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Thanks for the info. I wasn't sure if they could fail in that manner. I guess I'll be ordering some new parts for it.

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1998 E320 Wagon

1992 300D 2.5 TURBO

1991 560SEL M119.960

1986 300SDL TURBO

1992 500SL Parts Car

1991 420SEL Parts Car

I have only once ever had a w126 module fail that couldn't be repaired by either re-soldering cracked joints, or replacing aged electrolytic capacitors.

Of particular importance when you replace the capacitors is to choose ones with the highest temperature rating possible. 105C should be the minimum temp rating for automotive use. Also, be sure to observe polarity!

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-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Good thread, i'm in the process of getting my cruise control to work.

Hilariously, I can make the car move faster with the cruise stalk but the speed never sets which leads me to believe it's a bad amplifier.

I'm going to go to the salvage yard tomorrow to try and pick one off of a car. Here's hoping I can find a good one!

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-Typos courtesy of my mobile phone.

I'm not confident I can choose workable alternatives. As always any help is much appreciated.

I'm aware the OP here is very old so if anyone can share their opinion on a particular brand of capacitors which have longer lives that would be fine too.

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84 300SD
85 380SE
83 528e
95 318ic

Hi Clemson!

Here is an updated list of capacitors:

For the 22uF units:
https://www.mouser.com/ProductDetail/647-UPW2A220MPD

For the 10uF units:
https://www.mouser.com/ProductDetail/647-UPW2A100MED

For the 2.2uF units:
https://www.mouser.com/ProductDetail/647-UPW2A2R2MDD

These are all radial type capacitors but the leads are long enough such that they can hit the holes on the cruise amp boards!

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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

Thanks for the new information on the capacitors. I still haven't gotten around to fixing mine yet.

My two cents, send it JamesDean, he'll fix it right for a very reasonable price.

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I'm old and have nothing to do but piddle with my car. I know that I could have gotten a great job from James Dean and I'll probably spend more on the workstation than he'd charge.

I could have gotten that PS gearbox rebuilt by a trusted member here, a good set of injectors from another and probably found a member who would have done the wiring for me when I put the 617 in the gas body.

What would I have done for the last two years had I not wasted them learning to repair my own stuff?

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84 300SD
85 380SE
83 528e
95 318ic

Thank you, JamesDean. That's kind of you and I'm obliged.

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84 300SD
85 380SE
83 528e
95 318ic

Subscribed

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

If I may suggest:

I checked all six caps before ordering new ones.

You can check the four axial caps but popping one side. The two radials do need to be removed completely.

In my case, they all speced even though the cruise control was not working. After checking/verifiying specs I soldered them back in and also resoldered the transistors, which looked a little suspect. That's all I did, and the cruise control came back to life.

IF the caps last at least 1000 hours and you use your cruise at 60 MPH, the caps should go 60k miles. If you use your cruise control 10% of the time....well, you do the math.

Bear in mind that the heat of un soldering could activate a dormant capacitor. Best to change them anyways. They are going to fail with age at some point. They are also inexpensive.

That the other board components seem to in general survive the years is to me quite amazing. Working on electronics fabricated in Europe years ago was not that pleasant.

The largest concern in Europe sold things in north America that had poor overall reliability. Phillips color televisons built there were a disaster basically. They had to withdraw them from the north American marketplace.