Cruise Control Issues
 

Hello to all!
Hope everyone has had and continues to have a wonderful holiday season!

I've got a 1991 300E with approx. 195K miles on it. Wonderful car; just painted and in wonderful condition. I love it.

My cruise control has not worked for approx. 2 years and after a recent 300 mile trip, I've decided to check into it. Maybe someone can help.

Cruise engages when the stalk is pushed up to accelerate; engages when pushed down to decelerate, and pulled in to resume. In each case the CC engages and the car speeds up for about 3-5 seconds and then disengages.

Any ideas?

Nick

Anyone?
 

Can anyone help with cruise control issue?

There was a past thread dealing with speed control on a W123 that could be repaired using an after market model.

The thread showed how and where to replace the amplifier and patch into the stalk/control. Check the search function.

Cruise Control. One of my favorites.

Yes... do search the forum. There are several options:

1.) if you are good with a soldering iron, you can retouch all the connections with a 35 watt solder iron (pencil type) and that will fix it about 75-80% of the time. Based on your described behavior, your CC is a prime candidate for this technique.

2.) Get an after market rebuild at about $270. Advantage here is there may be a warranty.

3.) If you are looking for true MB OEM, it is about $600 from the dealer as they want to sell you the brain and the Control Chip.

Location of Cruise Module:

once you remove the knee pad under the steering wheel, you will see a silver box 6 inches long, 4 inches wide and about a 1 inch thick held in by two 8 mm bolts. That is the CC brain.

Good Luck

meh. Go to a junk yard, find any mercedes from 80 to 91, pull the cruise amp from underneath the dash. Call it a "Large Relay" Pay your 5 bucks and go plug it in.

How to: Find any 124 or 126 (123s are too old for this type of work) - pull the lower kickpanel by flicking off the plastic covers on the left and right side, get out your phillips head (cross tip for those of you in St Lucia) and unscrew the 4 screws..PULL....pow, the whole lower kick panel comes out.

on your knees...duck you head in and under the dash...look up..you should see a relay about the size of a VHS tape....take your flat head screw driver and flick off the clip that is holding it onto a frame. and just pull the cruise amp out. "Large Relay" at pull a part is 5.50 with warranty....GET THE WARRANTY...its five bucks...but your cruise actuator could have failed...pulling 2 or more amps and frying your new to you amplifier.

better to get the ones with the small black relay on the bottom. They are newer and usually operate WAY better. After you do that, and you still have a problem, then go to GDL online and print the troubleshooting portion, get out your multi meter and check ohms and amps.

Peter @ gdlonline rebuilds amps...I have one that he rebuilt and I haven't had a problem since.

I have swapped his out with the late 80s early 90s versions and they work great too.

If you can't find one that works at a junkyard then buy one from Peter. You won't be disappointed. Peter may also be the nicest guy on the planet...I can't be sure...but I think he might be.

Feel free to pm me and we will have a hoot and and hollar matching your symptoms to one of the three possible issues. Amp, Stalk, Actuator.


Kent

Thank you for the advise!

Before doing all this check your brake light switch at brake pedal. It might be sending very low current which in turn will disable cruise control.
I had same problem with w124 and after replacing switch from ebay($12) my cruise is working good.
On w126 on other hand it's not working so i have to get amp from jy.

Remember one thing:
Before assuming extreme check simple and cheap things first respectively and if it's not it go for complex and pricey procedures.

He's getting some response to it. That would rule out the brake light. Brake light gives the whole amp a key ground. If it were the brake light he'd be getting nothing. Because he is getting surging and weirdness, it points to first the amp, then the stalk. Probably not the actuator unless its pulling just enough over amperage to weaken the solders in the amp.

OK

How's everyone doing? Hope you all had a great Thanksgiving.

Back to my cruise control issue. As I stated above, my cruise would engage for about 2 seconds and then disengages. The accelerate mode works.

Yesterday i found a amplifier at a pick and pull, installed it, and now nothing on the cruise works. Any ideas?

Amp
 

Finding a good working used amplifier is going to be hit and miss. I am looking for one too. Thinking of spending more to get a rebuilt one with a warranty from a trusted vendor.

It was $10 at the pick and pull. Had to take a chance.

Coding Attachment
 

Interesting.....................

Read in another forum about many issues with cruise control modules are not only the amps but the coding module attached to the back. I bought a used amp with a coding attachment off Ebay (cheap) and it has worked a lot better than mine which was pretty shot. Although the replacement worked, it would have an annoying "hunting" motion that pretty much negated it's use.

I took the original coding attachment off my shot amplifier and put it on the replacement amp and now everything works perfectly! Let's see how long this lasts since these old parts are very cranky! LOL!

The picture shows my original coding attachment on the right next to the replacement. The numbers are a little different.

What is that "coding" thing for? I re-soldered mine. But had no clue to its use.

Coding Attachment
 

I may be way off on this but it is my understanding a lot of these cruise control amplifiers are "universal" and may fit other makes and models. The coding attachment from Mercedes is the "brains" that will make it operate for our specific model.

In my case, it appears my original amplifier was the issue. The replacement amplifier was OK but the coding attachment was the issue. Switching the coding attachment appears to have solved my problem, at least temporarily. You never know with these old parts!

I believe it was the GDL website that also mentioned coding issues account for many cruise control problems along with the amplifier.

Ah. That makes sense.