[talldarktexan]

hi all,trying to diagnose the cruise on a 85 380sl.looking at the actuator in parts they call it a vacuum actuactor.that confuses me. it has no vacuum hoses going to it and it does have an electric motor on it. can any one explain this.....does the motor run an internal vacuum pump? is there a diaphragm inside or what?????? I have Mitchell on demand but can find no info on how the actuactor works. please help

 

[rowdie]

The Mercedes part catalog calls it Control Unit / Actuator. No mention of Vacuum. The early models used vacuum.

 

[okyoureabeast]

Your cruise control on your 85 380SL is electronic. No vacuum needed. The actuator is controlled by a electronic module that lives under the driver's side kick panel. Upper left side under the panel. It's a big black box.

Generally, when cruise doesn't work it's this brain that goes bad. German electronics from the 80s are crap. However, it's easily remedied with a steady hand and soldering iron. You're also welcome to contact Kris at this website for his repair services. His forum moniker is James Dean. Awesome services.

Vacuum isn't driven by a pump but by the sucking nature of these engines on the intake. IE, engine needs air for the cycle and that sucking air is what makes the vacuum. Rowdie will no doubt correct my understanding of how this all works and I await his reply with anticipation

 

[Ruindr]

Kris has an excellent web page with testing procedures. +1 on awsome service, and cheap too.

www.cruisecontrolrepair.com

 

[talldarktexan]

thanks for the reply. yes I know how the vacuum is created.and the actuactor indeed looked to me to be totally electric,but the parts books keept calling it a vacuum act..i do appreciate your conformation. most cars I deal with are American and most of them still utilize vacuum servos up until electric throttles took over....man, ill take a car with a throttle cable over throttle-by-wire any day of the week. just my opinion. thanks again for the reply,barry

 

[talldarktexan]

cool,i was looking at after market suppliers.live and learn. I have often wondered why the service book and the parts book will call the same part different names.ford was always been bad about that.

 

[joser85]

A quick shout out to Kris AKA @JamesDean for solving my non-functioning cruise control. I shipped Kris the speedo, module, and actuator and in a very short period of time he identified/fixed the issue and returned everything to me. My mechanic, Tom, and I replaced everything, and voilá, CC is working great! I highly recommend Kris if you have CC issues.

Now I just need to go cruising on a nice road trip! I'm really going to enjoy the accel/decel control, which strikes me as having been ahead of its time back in 1985, although my cursory google search yielded no verification of when the first accel/decel stalk appeared. Maybe someone else knows?

Another interesting observation: I noticed that my accel/decel stalk works differently from any modern cars I've driven. In my experience, in modern cars a nudge on the accel/decel stalk (or buttons) changes speed a pre-determined interval, i.e. ~2 mph, and no more or less. By contrast, in my SL I simply hold accel/decel as long as I want until it reaches the speed I want, at which point I let go and the speed is maintained. I actually like this better, as I can nudge the stalk just once to reach the desired speed, whereas on modern cars I must nudge it multiple times to reach the desired speed when the desired speed difference is greater than the pre-determined interval.

So there are my cruise control thoughts for the day.

 

[reno4u2]

Cruise control actuators can (but rarely) fail. That's why you always see them (and power steering pumps) at salvage yards...nobody needs one. My very UN-sciencetific analysis...lol. IIRC there is a small arm that rides on a (looks like plastic) ribbon. The ribbon is what wears out.

 

[rowdie]

A quick shout out to Kris AKA @JamesDean for solving my non-functioning cruise control. I shipped Kris the speedo, module, and actuator and in a very short period of time he identified/fixed the issue and returned everything to me. My mechanic, Tom, and I replaced everything, and voilá, CC is working great! I highly recommend Kris if you have CC issues.

Now I just need to go cruising on a nice road trip! I'm really going to enjoy the accel/decel control, which strikes me as having been ahead of its time back in 1985, although my cursory google search yielded no verification of when the first accel/decel stalk appeared. Maybe someone else knows?

Another interesting observation: I noticed that my accel/decel stalk works differently from any modern cars I've driven. In my experience, in modern cars a nudge on the accel/decel stalk (or buttons) changes speed a pre-determined interval, i.e. ~2 mph, and no more or less. By contrast, in my SL I simply hold accel/decel as long as I want until it reaches the speed I want, at which point I let go and the speed is maintained. I actually like this better, as I can nudge the stalk just once to reach the desired speed, whereas on modern cars I must nudge it multiple times to reach the desired speed when the desired speed difference is greater than the pre-determined interval.

So there are my cruise control thoughts for the day.

My 2008 Edge and 2004 truck must be old. I can accelerate to the speed I want by by keeping the cruise button increase depressed.