Aftermarket Cruise Control for MB
 

I did this a while ago but I am just getting around to posting about it. I installed a Rostra Globalcruise unit in my 300D. I got it from a local car audio/accessories place. The instructions are written with a pro installer in mind so they assume you have a clue. It was fairly simple to install with just one unit under the hood. I tied into the factory CC power supply and attached to the brake switch by soldering into the factory connectors. The control stalk looks decidedly non-MB but since it is mounted low under the column you don't really see it. The stalk is a bit of a pain to install and required removing the entire turn signal stalk to drill the hole and tighten everything up. Careful when you adjust the CC stalk to the correct angle, the wires are thin and will bind/break if you don't make sure they have enough slack. I also removed the factory CC switch and give it away. Also underhood the factory CC actuator, mount and linkage have all disappeared. The speed sensor is a simple magnet/coil affair mounted on the driveshaft right behind the tranny. It is actually a lot easier to install than you would expect. Sorry, no pic. Didn't feel like jacking up the car! Hooking up the cable to the MB linkage is a bit difficult. I ground off one of the "ball" fittings and punched out the remains so I could use the hole for a mounting screw to attach the cable. A small custom bracket bolts to the valve cover to retain the sleeve. The unit/brain itself is simply bolted to the inner fender. I routed the wires though the firewall at the rubber bulkhead grommets and covered the wiring with black plastic wire loom. How does it work? Great! The only negative is a slight hiccup when transitioning from an upgrade to a downgrade. It keeps accelerating then backs way off on the downhill then too much throttle. The result is a small surge, usually just one and only on mild transitions. There is a "gain" adjustment that may smooth this out but I haven't messed with it yet. The best part is the price. I paid @$250.00 w/tax. Install was about 2.5-3hrs working with beer in hand. IMHO, a viable replacement/alternative to repairing the MB system. RT

cool...I have ben contimplating something very simmular for my W116 if resoldering the old one doesn't do any good. THe cruise in my W123 has turned out to be intermittant....but then the seller said it didn't work, but did on my test drive.....may do the same for it too if a resoldering doesn't fix it too.

since rwt's old CC switch is residing in my car for now i'll say thanks! again and great you got that aftermarket CC working.
looks like a neat setup. maybe being controlled by wire is more stable than the original actuator/linkage way?

:cool:

You can replace the factory cruise unit in your car for about $150. No fuss. No muss. Don't understand why you would go through all of that trouble and expense unless your car didn't have a cruise control to start with.

Len

Where have you seen Cruise amps for about $150............with guarantees.

You can replace the factory cruise unit in your car for about $150. No fuss. No muss. Don't understand why you would go through all of that trouble and expense unless your car didn't have a cruise control to start with.

Hahahahahaha! What planet are you on? A rebuilt cruise amp will set you back $300 and thats no guarantee that the actuator, switch, etc. aren't the problem. Nor does it guarantee it will stay fixed. I tried the resoldering. I tried different cruise amps. So I should install a new factory unit and have ti go south all over again in time? GDL wants too much money with no guarantee it would fix my issue. I have knee problems so driving more than an hour without CC is painful. After replacing the cruise amp a few times and fighting with the silly brackets/inaccessible bolts this rig installed in about the same time. It works. Locks in the set speed and does what its supposed to. No cutting out, no repeated surging, etc. No fuss, no muss. RT

Beckman Technologies rebuilt my CC brain for 150 and they warrantee for one year. Just make sure you diagnose the right problem.

Well, guess it's been a few years since I bought one. The last one I bought for my 240D cost me $129 directly from Beckmann Technologies, http://www.beckmanntechnologies.com/products.html. I just looked at their web page and prices go from about $250 on up to $500 depending on model. Beckmann also took back a unit that I bought from them because it wasn't the problem. I believe they guarantee their units too. I've got a catalog from George Murphy, Performance Analysis, and he lists his as starting at $149. Don't know how much yours would be. George can be reached at George_Murphy@compuserve.com.

Sorry for the post - got to catch up with the times I guess.

Len

And at those prices its cheaper to put an aftermarket unit in that will likely be far more reliable.

At $150 its a tough argument.....At $250-$500 its a hard argument to justify staying stock.

Sokoloff,
I have no issue with those that choose to stay stock. I suppose there are reasons to. I just wanted to show that there are alternatives to MB's notoriously tempermental CC system if you are completely fed up and have to have CC like I do. I would have gone stock if I thought it would work but the aftermarket was a better choice for me. RT

I dunno how long ago you actually did it, but you should have searched this forum first...

I installed the same unit into my 300TD last year and posted instructions on how to wire it up to the factory control stalk AND how to use the original cruise control's VSS signal instead of having to install another speed sensor. Also, I discovered (too late for myself, sadly) that Audiovox sells the exact same unit (rebranded) for almost half the price.

If you still want to do either of these things (if you can get your original control stalk back) I can dig up the thread for you if you like.

For anyone out there with doubts, let me also add this thing is GREAT. My cruise is perfectly smooth and I no longer have to worry about the antiquated original cruise control dying yet again. I went on a 11,000 mile road trip last summer and used it the whole time without a single hiccup.

I'm glad that worked for you. I hope the newer aftermarket CC units are more reliable than they were years ago--those were pure junk. I've been toying with the idea of retrofitting a much simpler VW/Audi CC system into my 123. These should be able to utilize the stock VDO speed sensor, and mount up to the same throttle linkage ball joints as well. I've owned two Vanagons with factory CC, and both have given me no problems whatsoever. I think the components might run around $20 at the local Pick-a-Part yard.

81Wagon,
Yes I did several searches but didn't come across your posts on aftermarket CC. I don't care if I use the MB stalk or the aftermarket as long as it works. I am interested in how you tied into the factory MB VSS. Instructions on how to do this would be great. I posted a while back looking for how many PPM the VSS produced to see if it was even feasible to hook it up to the aftermarket CC unit and no one responded. There are many multiplier switches so there is a good chance the aftermarket will work with the VSS. Thanks, RT

The VSS in 123's sends around 8,000 ppm. In my car, the signal came to pin 11 on the factory cruise amp (I think it was a green wire). The cruise amps in 123's did change at least once though, so yours may be different. Check a wiring diagram.


(The first post on the third page of this thread contains my instructions for wiring up the factory control stalk.)

cool info...will try to resolder my amp and if that doesn't work then I go this route....