Cruise Control Again - PeachParts Mercedes-Benz Forum

Nashvillecat · #1 03-23-2006, 08:01 PM

I have a 83 300 DT and the cruise control is completely dead. I took off the amplifier under the dash board as was suggested in this forum and the solder connections all look good. Are there any tests I could do to the board? or could the problem be the switch? And how do I test the switch?

Thanks

Nashvillecat

pawoSD · #2 03-23-2006, 08:13 PM

Thats interesting, I have the same issue, and I just swapped in a supposedly working new (used) cruise amp about an hour ago, and it still does nothing.

The connection (pins/plug) in the dash look clean and fit well, so I am doubting its a connection issue down there, but in the engine compartment I had some corrosion in the plug for the acutator, so I cleaned it a bit with some Deep Creep Penetrant/Cleaner, when I plug in the acutator under the hood with the car on it makes a "ckkcckckckkk" clicking/grinding sound if I do the plug unevenly. Jamming it straight in results in no sounds/movement from it. I also have an extra acutator that is tested to be good (looks very clean too) and when plugging it in in the same way, it does the same clicking and grinding noises if I do the plug unevenly. With either one hooked up triggering the stalk does nothing at all, even when driving.

Before messing with the system, I could be on the freeway and once in a blue moon it would "engage" if I hit the stalk to accelerate, but would drop off again as soon as I let go, or, *sometimes* it would absolutely floor the pedal, and take off like no tomorrow without letting off (had to hit brakes or cancel on the stalk) This leads me to believe I don't have a dead stalk/switch, nor acutator. The amp was known to be working, but still nothing when its installed.

Any ideas? I really want this to work, and yet even with BOTH components swapped it doesn't do anything.

Targa-NF · #3 03-23-2006, 08:23 PM

I just got a " new to me " 81 300SD. The cruise control in unpluged.

I am dying to plug it in and see what is going on. It is like having a big RED
BUTTON under my hood. I am trying to contact the guy who sold me the car
too see if he knows why is not hooked up. Also my black 300SD, If I set at
65 MPH it is very choppy. It will not sit at 65 MPH shoothely. It will give gas,
then slow. then give gas, then slow, every few seconds. It was working well
over the summer and it not worth using. Sorry to add a question on your post
Nashvillecat. Thanks. Jay

81 300 SD 138 Miles " Black "
81 300 SD 134 Miles " Diamond Blue Metallic "
81 300 SD 237 Miles " Diamond Blue Metallic "
83 300 SD 166 Miles " Cream "

NoCalMer · #4 03-23-2006, 08:27 PM

Even though the solder joints look good I would resolder the whole board. My board had like a clear film they put on after soldering the whole board which I think caused cold solder joints. I resoldered my whole board it works great now.

donbryce · #5 03-23-2006, 08:30 PM

I'm no expert, but the symptoms described sure point to the control box board solder joints. I too eyeballed the thing and nothing stood out as cracked, burnt, broken, loose, or anything. I set up a nice magnifying glass/light, used a low heat fine point iron and spent about 1 1/2 hrs remelting all the connections, except the ones directly to the integrated circuit 'things' (black boxes), as I read that they can be ruined with too much heat. Long story short, it works great now.

NoCalMer · #6 03-23-2006, 08:34 PM

Quote:

Originally Posted by pawoSD

Any ideas? I really want this to work, and yet even with BOTH components swapped it doesn't do anything.

I had the same problem after I resolder the major connections on the board. It would work sometimes and was flakey.I resolder about ever connection on the board and it works great now and engages easily.

pawoSD · #7 03-23-2006, 10:12 PM

But the one I got (from Jim here on the forum) was said to be in working condition when pulled, then it was shipped to me, and I installed it, and it does nothing just like my old one...could it be anything else?

Taking that thing in and out is a pain, thats for sure....I guess I have nothing to lose in trying to resolder, I'll get a low-heat solder gun and work at it on Saturday.....

kmaysob · #8 03-23-2006, 10:28 PM

Quote:

Originally Posted by donbryce

I'm no expert, but the symptoms described sure point to the control box board solder joints. I too eyeballed the thing and nothing stood out as cracked, burnt, broken, loose, or anything. I set up a nice magnifying glass/light, used a low heat fine point iron and spent about 1 1/2 hrs remelting all the connections, except the ones directly to the integrated circuit 'things' (black boxes), as I read that they can be ruined with too much heat. Long story short, it works great now.

cold solder joints dont allways have to look bad. i resoldered on of mine that looked perfect and for 40+ cold solder joints. i have also found that a thermal controled solder station works a hell of alot better than the standard plug in. i know its not in everybody budget but it was the best 120 bucks i have spent in a while

pawoSD · #9 03-23-2006, 10:59 PM

Is there a particular soldering iron/gun wattage that you'd recommend for remelting these joints? I have a 30watt gun, and I bet that'd be way too hot....I'd like to do this saturday, I'm thinking more around a 15-20watt gun or something to protect the board from too much heat....

If I tear all that apart again and resolder and such and it still doesn't work I am not going to be happy....

kmaysob · #10 03-23-2006, 11:15 PM

i really couldnt tell you by wattage. mine is measured in degrees. the tip i am using is a 800* tip. i know the standard plug in pencils cool off instantly when the tip is touched to the joint.

SD Blue · #11 03-23-2006, 11:58 PM

[QUOTE=pawoSD]Is there a particular soldering iron/gun wattage that you'd recommend for remelting these joints? I have a 30watt gun, and I bet that'd be way too hot....QUOTE]
Most pencil irons, such as Weller, have interchangable heating elements. The standard wattages are 23,33, & 45 for circuit board work. I generally use a 33 on most circuit boards of this era. The size of the components and lands usually work best with this wattage. I wouldn't however recommend a gun as it is just too awkward. A good Weller soldering iron will cost you about $35-40 ($14 handle, $25 heating element, $5 ea. for tips) The good thing about using this kind of set-up is you can add different heating elements and tips for other uses down the road.
Handle:http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=363899&e_categoryid=123&e_pcodeid=57803
Heating element:http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=253022&e_categoryid=123&e_pcodeid=57803
Tips:http://www.mouser.com/index.cfm?&handler=data.listcategory&D=*578pl113*&terms=578-pl-113&Ntt=*578pl113*&Dk=1&Ns=SField&N=0&crc=true
(click on the pdf file for pics)

pawoSD · #12 03-25-2006, 01:31 AM

I did some more messing with my cruise today, the new (used) box I got from Jim here on the forum is from an 83, the box itself is smaller (about 2cm shorter) and weighs close to nothing (I'm guessing the electronics shrank a bit

) So, with that one in, the cruise would do nothing at all, not so much as a quiver. I got annoyed, once again tore off (gently removed while frustrated

) my lower dash cover and pulled it out. Earlier in the day I had bought a 15watt soldering iron (pencil style) and some flux...electrical contact cleaner....etc...and had opened up the older/bigger/heavier cruise that was "original" to my car. As I inspected it, I saw it was from December 1985! My car is from April 82....so this was definatley replaced back then (probably under warranty! wow!) anyways, I bent back the little locking tabs, and slid out the circuit board...wow....talk about pre-historic.

It looked like something you'd have found in a tv in the 1960's or something....

Soo...I melted and re-set a ton of the solder connections on the board, added a little flux to some of them, finally put it back in its case, bent the tabs back as best as I could, and cleaned off the pins super good with contact cleaner and a towel. Put it back into vehicle, tried it, it worked! However, its still very, very fussy. At lower speeds (35-50ish) it hunts for the crusing speed. If I set it at say.....45mph, it will after a couple seconds, grab on and hold it there, but then it will accelerate to 50 (always does it in 5's) violently, it downshifted!!!

then when it hit 50, it drops the pedal to nada, coasts back to 45, and then violently roars to 50 again, repeating this over and over. At higher speeds of 65+ it seems to hold very well, and even adjusts to hills and changes in speed properly, rarely does it do the hunting, and when it does a quick flick to "accel" makes it stay where it is and behave. In my test run I went about 8 miles nonstop at 73mph and it held it like a stone. If it can do that I will be a happy person. I have yet to take a long enough trip to make a good test of it, but it seems to work at those speeds. It used to not work at all or ocassionally "floor it" if I tried to engage it, so I guess this is a definate improvement. It probably needs to be rebuilt....right? I'm guessing some of the items on that circuit board just aren't what they used to be, and could probably stand to be replaced......I'm planning on it sometime in the semi-near future if my funds will allocate for it.

So overall, replacement cruise was useless, worked on old cruise, got it to work reasonably well (for now).

Part numbers: The one that was in my car, though a 1985 replacement part, had the following numbers: 412.205/7/7 then a bit below that it had: 003 545 86 32

The replacement one I got, was physically smaller, and dated january 1983, had the following numbers: 412.205/1/1 and the lower number: 0015457932

Any idea why the replacement one didn't do anything? Supposedly it was working, though it may not have been. Both boxes have 14 pins, this led me to think they'd plug in/work the same too?

This was a very long cruise control related post, any comments??

RUN-EM · #13 03-25-2006, 07:59 AM

old truck driver's cruise control......the chopped off broomstick between the seat and the accelerator

Justa idear ya might wanna keep runnin around, ya know, fer when ya get tired of playin with th electronic marvel

Please do not regard this as a serious alternative

Just stick your leg up here again, and I shall give it another pull

Regards

RUN-EM
1983 300SD- aka - SPARKY THE DIESEL

my123ca · #14 03-25-2006, 08:51 AM

There might be something wrong with with the vehicle speed sensor. Its the little black box behind the speedometer. If you remove that sensor, you'll understand why it does it in increments of 5.

You might find this ridiculous, I had problems with my c. control too. It only engages once when you are driving. It wont re-engage once you disengage the cruise or step on the brakes. It was also little bit rough when it is engaged. Speed adjustments were really abrupt. It felt like someone would floor the brakes to lower the speed or floor the accelerator to increase the speed. I found out that someone had replaced my stop light with a two filament bulb. Dont ask me how it fit there, but once I replaced it with the proper bulb, the cruise control worked fine. Speed changes were not neck breaking anymore and it would engage anytime.

signalredcoupe · #15 03-25-2006, 08:55 AM

I have had the same symtoms with my current coupe & the 240D I had. I've yet to do the resoldering routine, but with what you're describing even after doing so, I'm wondering if it could be a combination of the computer & the speed sensor screwed onto the back of the speedometer? Paul.

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'84 300CD 290,000