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Garage => Mechanicals => Topic started by: jtwoods4 on 20 January 2020, 01:05 PM

Title: Cruise control 1980 300sd
Post by: jtwoods4 on 20 January 2020, 01:05 PM
Hey guys does anyone have experience with replacing the cruise control amplifier in a 1980 300sd? My car will not hold the speed however it will accelerate if I press the cruise control or lever up it just won't hold that speed. I guess the only thing to replace is the amplifier under the dash. Anyone have experience with this?
Title: Re: Cruise control 1980 300sd
Post by: daantjie on 20 January 2020, 03:12 PM
I rolled the dice and changed out my amp to one of the Programa units.  Before it did not work at all, could not set or hold speed, and afterwards it worked, however I find it very jerky, and it constantly surges and backs off to try and keep the speed.  I don't use it anyway so it does not faze me but it really is not pleasant and makes me feel seasick after a while with all the hunting it does :-\

Here is the one I got for what it's worth, from amazon no less:)

https://www.amazon.com/ProgRama-W0133-1602706-PRO-Programa-Control-Amplifier/dp/B001G65F7K
Title: Re: Cruise control 1980 300sd
Post by: jtwoods4 on 20 January 2020, 03:15 PM
What is a program a unit can you send a link? I need to get this working I go on long road trips and it's very uncomfortable driving these cars long distances because your knee is always bent on the gas pedal.
Title: Re: Cruise control 1980 300sd
Post by: daantjie on 20 January 2020, 03:15 PM
What is a program a unit can you send a link? I need to get this working I go on long road trips and it's very uncomfortable driving these cars long distances because your knee is always bent on the gas pedal.

Just updated my post with a link.
Title: Re: Cruise control 1980 300sd
Post by: jtwoods4 on 20 January 2020, 03:17 PM
Thank you!
Title: Re: Cruise control 1980 300sd
Post by: TJ 450 on 20 January 2020, 07:18 PM
If you're at all experienced with electronics, the units are easily repaired most of the time. As the electrolytic capacitors dry out this contributes to surging as the component values are no longer up to the task. Dry solder joints are also another issue.

They were always notorious for minor surging though.

Tim
Title: Re: Cruise control 1980 300sd
Post by: jtwoods4 on 20 January 2020, 07:27 PM
I will take it apart and see what I can do.
Title: Re: Cruise control 1980 300sd
Post by: OLDGOLD on 08 May 2020, 09:32 AM
Let me know how it goes! My 300SD does the same thing. I'm tired of my right calf seizing up after a long drive lol
Title: Re: Cruise control 1980 300sd
Post by: ptashek on 08 May 2020, 01:04 PM
Follow this thread, and you should be able to get it fixed:

http://forum.w116.org/mechanicals/cruise-control-not-keeping-set-speed/

The diesel unit is different to petrol units, but would have the same issues.