I have an 86 300E. Will the control amps with the little relay on the back work on my car? Mine doesn't have that relay on the back. I think the relay is a "coding" relay. The 14 pin plug looks the same however.
Thanks

 

OK, I see a few viewers but no responces. I need to replace my cruise amp. There are several on ebay, 3 are shown with that little relay on the back. 1 is shown axactly like mine (no relay).
Question is: Are these control amps interchangable?
I'm new here, but I have considerable knowledge with cars and may be able to help many of you guys in the future. I just need some quick help right now................anybody?

 

Welcome. Just a couple things.

First, I have no idea how to answer your question.

Second, this forum is fairly active but you have to give people more than 2 hours and 15 minutes to answer you before you assume people are ignoring you.

Perhaps you should do a search over at www.mercedesshop.com. They have a great technical forum. If you can't find your answer after some searching, start at thread. You will probably get some good responses. Good luck! Sorry I couldn't help.

 

Thanks BigPete123. I'm used to the cobra forum which is very active, usually just a few minutes for a responce. I'll take your advice.
Thanks again

 

No prob. Now post some pictures of that cobra!

 

do some searching on the forum. Many people have found that the cruise control amps just need some resoldering inside to fix them.

Search here and on mercedesshop.com

Alon

 

This forum is very active, it was just a weird question, that's all.

 

Thanks everyone. I had already soldered the curcuit board with mixed results. That is, it would act weird when engaged. So, I was considering just replacing the cruise control amp. I found several on ebay and wasn't sure if they would work since they looked different than mine, mine doesn't have that relay on the back.
Well I decided to re-solder the curcuit board again using a 4" magnifing glass to better see the board. Under careful examination, I observed a broke wire going to one of those 3 legged diode looking things. Re-soldered that and all other points again and now cruise is working fine as it should.
In retrospect, I guess the answer to my question is "no". I have no idea what would happen if you installed an amp with the "coding" relay into a vehicle that did not come with that type amp.
I wasn't willing to pay that much to become a test subject, maybe some else has tried it with good results. That's what I was wondering.
I've only had the car 1 month, but by lurking the forums I've been able to easily repair the odometer, fan sensor, and now the cruise, none of which worked when I bought it.
Thanks everyone!

 

Still wondering if anyone has installed a cruise crotrol amp with coding relay attached, into a vehicle that did not come with that type of amp?
If so, what happened, did it work......did it act weird.......did it do nothing?

Surely, someone has been brave enough to try it, what could it harm?
What if the relay is removed from the amp, would it still work?

If no one has tried it, I might be willing to, in the event it could help others. But, if it has already been done...........I'd like to know.
Thanks, Perri

 

is your cruise control acting up again?

 

Nope, it's working perfect. I suspect that at some point it will fail again. At least that's what I've read here. Given the newer amps ARE different, I assume they might be better or upgraded and may not experience the problem as the older ones do. I just don't know what that relay on the newer ones are for.

About soldering the card. I have a method that I learned from an electrician here at work. I know I'd get bashed for suggesting it, but I've never been real good at soldering. By using this method, you'll get super results that'll make you look like a pro. And that cruise control is going to work when you're done because the solder points will be tight and just as pretty as new.

 

do you mind sharing? My cruise control pooped out and since I do almost all city driving, I haven't bothered with it. But this might be a nice evening project for me. I suck at soldering bigtime and I always get frustrated.

For resoldering, do you simply touch the tip of the soldering iron to the old solder points, melt then, back off, and let them dry? Or is there something more to it? Thanks!

 

OK Pete, I'll probably get bashed for this, but here goes. You first need a decent soldering pin, not a soldering iron. A soldering pin is cheap, maybe less than $10. Get one with a sharp point, not flat.
The point itself is about 1" long and less than 1/4" diameter.
Get yourself a big magnifing glass, it's best to make it stationary if possible, so you don't have hold it with your other hand. Get yourself some good light.

Now get a little sponge and put some battery acid on it. Just 10-15 drops in the center of the sponge. There's plenty of old batteries laying around, use a eye dropper or put your finger on the end of an old straw and draw out a little.

I didn't clean the varnish off of my curcuit board, I used the soldering pin to kind of melt it off each point. But guess what? That leaves the soldering tip contaminated.

Take a knife and scrape that crud off the tip so that it looks like copper again. Now wipe the tip on the acid wet sponge. It'll clean the soldering tip off and allow a quicker and better melt.

I know, I know,........sulfuric acid and electronics DON'T MIX. Don't worry, you're using the acid to clean the tip. And while there is some minute, residual amount left on the "very hot" tip, it will only serve to make a better joint.
**(Use at your discretion, I perfer to have my cruise work)**

Start at one end of the curcuit board and work your way down, just hit them all, even the little ones on the long chips. If while doing this you notice that some points end up as a hole, flip the board over and you'll probably see that there is nothing on that particular point anyway.

After you hit them all, check to make sure that you did not bridge 2 points together. I found that I could'nt use the soldering pin to unbridge them, they would just rebond. I used a dental tool with a sharp point, heated it with my propane torch until red, and pulled it between the 2 points and presto!

And yes, I just touched the little points and watched for it to melt, pulled off the soldering tip and allowed it to cool. Takes about 10-15 minutes to do the whole board.

I've used this procedure to repair the main relay on several Honda cars. It might be possible to repair some of these MB relays as well.

Sorry for being so long. Take your time, use some acid, and enjoy your cruise.
Perri

 

Cool, thanks!