Okay, I've pulled mine out and it's not so much a plasticy film as a shiny lacquer sort of thing. And I know you've seen it, because the picture you posted earlier shows it on the circuit board :-).

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'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)

Ok, gotcha. Just solder through it. The rosin in the solder seeps up and is just generaly messy looking, but does not really hamper the process(untill it gets in your eyes or you breath enough of it). Unless you have something odd, go for it.

Two worthwhile things to have for this are a vacuum de-soldering tool, $10 or less at RadioShack, it's a spring loaded tool that sucks up solder when it's hot. This is handy if you bridge two joints(which is BAD) or if you have a perticularly nasty looking one and want to start fresh as it were.

Another, again cheap from radioshack, is a little can of soldering iron tip cleaner and tinner. You stick your iron in this now and again to clean the aforementioned rosin and crud from the tip and to re-tin(cover with a light coat of solder) it. It's hard to explain, but hot solder transfers heat much better than just the iron itself, so you want a light coat of solder on the iron at all times. Another method is to have a small little drop of solder on the iron, and touch that to the joint, letting them all melt into one another, reviving the joint. I also did a number on several iron tips during this, so if your buying new, make sure you can get replacement tips. Sears had non for my Weller, I was a little anoyed that I had to make some others work.

It's trial and error, and tedious, don't give up. I usually spend two hours on a box. If you have reading glasses, use them, or better yet is a lighted magnifying glass. Use GOOD lighting in any case. You'll find yourself turning the box this way and that way to get the best angle.

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

One of my early attempts at soldering an amp, whch was a quick and half hearted effort, gave me a badly surging amp. An imporvement since it did not work at all before, and it gave me hope. After throughly soldering it up again yesterday, it's one of my three working like a champ. Surging is almost always the amp, and can be bad joints it seems, but naturally I can't swear that's it. Take an iron to it, can't hurt..

I have another surging amp on the way from a friend here at some point, I'm curious to see what it does.

I do plan on writing up something on cruise servo testing and disasembly/lubricating. Some problems can obviously be caused by them, but as a man told me once, most of the cruise servo's left on cars in salvage yards or what have you are good by virtue of the fact that the amp went out so early in life, they have had little use.

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

Thanks Wolf, I'll now plan on taking the amp apart and I'll check the solder connections as well as the resistors you showed in an earlier photo. I have a multimeter that I can check shorts with as well.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

wolf_walker,

The cruise control on my SDL works intermittantly. If you're interested in working on a newer amplifier, let me know and I'll be happy to send it to you.

BINGO.
You hit the nail on the head, I adjusted the slack out of the cruise cable and it works well. One thing though, to remove the slack, I needed to unscrew the cable adjust bolt almost all of the way oul (only 1 1/2 turn left in nut) is this normal? is there another adjustment for the cable, in the actuator?

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

Wolf, I read your replies in your "Aftermarket Cruise Up And Running" thread but I decided it was more appropriate to add my reply here since it applied to the OEM unit.
I pulled my amp out and took the circuit board out of the box. I went over each soldered joint today with a circuit tester and found they were all good and there weren't any shorts either. It looks like I will have to check each individual component but I have no idea how I will check the IC's since my knowledge of electronics stops there.
I know it would be easier to go the aftermarket route but I have this thing about trying to keep a car all original, except for car audio systems but even there I won't cut interior panels to fit speakers.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

It's not too hard to check the switch and servo, GDL's oft posted site has the info. Don't be shocked if everything comes out ok and the amp is bad. I'm not convinced checking the joints with a meter would always show a bad one. Maybe, but it depends on how a circuit is layed out.

Checking the IC's, I'd just replace them there so cheap. Search Google for the part number, I found them all eventually.

Are you planning to try and diag and replace parts on your amp if need be? I'm curious how that would work out as I'm under the assumption that there indevidualy calibrated on the bench acording to what the specs of the specific parts in them happen to be. See the resistore on the little metal stakes? I think those are for calibration. Friend of mine came up with that threory, but I buy it completly.

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

Yes, I saw the resistors on the "stakes" I was curious about them being that way. I'm going to check what I can on the amp. I am even going to reference my electronics books that I have that might help me along the way. As far as the IC's go with all their many legs they have to solder, I will probably pass on trying to replace them as my hands are barely steady enough to solder single connections. So much for a career in brain surgery or any surgery for that matter.
I may just go for your aftermarket set-up.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

you can remove the plasticy film with Denatured alcohol, paint thinner or acetone and a Plastic brush It helps with soldering

http://www.mbca.org/pages/tech/MBCA_Troubleshooting_cruise_cont.htm

I had a site with pictures, I'll see if I can find it on the other computers..

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1999 E300DT (131,800) 154,000 Black on Black SOLD

2006 CLK 500 coupe Capri Blue on Grey (zoom,zoom)
47,000mi

04 VW TDI Passat 80,000mi
(Techno)

How to eliminate oil dependency through market-driven approaches.
“We could cut oil use in half by 2025, and by 2040, oil use could be zero,”
The Sound of Diesel Speed
Ode to MB

I figure I'll stab into this as well since I have some experience with the units...

...I think the general failure is a broken/bad solder joint where the connector eletrically attaches to the circuit board. Mine has this problem currently and just slightly touching the wiring harness or the unit itself hooks everything back up. ALso a good swift kick to the lower panel rocks the wires into position.

The actuators on gas and diesel models are the same. They just put them in slightly different places.

Are you telling me that they are directly driving the acutator motor with transistors? What type? Seems like too much of a load for even a basic transistor (atleast a switching one). Just wondering which ones it was in the picture.

I have an extra cruise amp as well that I got from the yard off of a 500SEL euro model.

The plastic film you guys are probably thinking about/seeing would be a clearcoat put over the whole board. I wouldn't worry about it unless you want to board to be spotless clean when you get done. Just burn though it and get your soldering game on.

Soldering is very easy to do and you might just try hitting up the connector end of the unit and doing those solder joints. This would eliminate the problem of having to worry about bridging joints, etc. which can be a byproduct of learning how to solder on something small

If anyone needs help and wolf is unavailable, I can offer assistance as well. Electronics hobbies are fun

I've had my 83 300SD ~ a month. When I got it, the cruise was working but
had terrible surge/retreat - unusable unless you like nausea.

I tried what Brandon said:
"you might just try hitting up the connector end of the unit and doing those solder joints"

A couple of those end joints looked flaky and I heated them. Also, I took a brass brush to the pins and female connectors hanging under the steering column.

Now, it is very usable...only a hint of surge. I'm quite pleased with this "limited" repair...if I took the soldering iron to the whole pcb, THERE WOULD BE some cut ray tracings.

I love to read about people willing to fix their Benz on their own, rather than pay the man big $$. Ive learned more about car mechanicals and electronics then you can possibly imagine, and its saved my as$ hundreds of times. I look at the cruise amp problem as an extension of my mechanical engineering undergraduate degree. Wish I paid more attention in the electrical classes!

So..Ive got my cruise amp pulled, I resoldered the board. No luck. Tested the actuator, examined the linkage, its all working well. Tested the combi switch on the steering column, works beautifully. Tested continuity based on the schematics, everything is correct. Still, no cruise.

So...I soldered a lead wire onto the amp pins on the PCB side. I now have 14 wires all numberered, taped onto my dash (no, Im not Christopher Lloyd from Back to the Future, just reeeeally curious).

So now, I can drive down the road, and probe each of the 14 connections on the fly to see what in the hell is going on, or, whats not going on.

All this to say, no cruise control presently. The amp gets power, grounds, gets all the inputs from the combi switch. Just doenst output anything. No actuator clutch voltage, no feedback, no actuator motor voltage. Nada. I set the multimeter to read AC voltage and seem to get 30-40 mA on the speed wire. Maybe I can set the multimeter to read frequency, as I believe thats what the speed wire inputs to cruise amp.

Im starting to wonder - is it possible to take my VW cruise amp and hook it up? Im more familiar with each of the 14 input/output pins on the benz cruise than I care to admit, and also have wiring schematics for my VW, as well as my Ford, Mazda, Jeep, Audi, and Honda. (I work on cars in my spare time, if thats not evident). Its all just 12v inputs and outputs right? My VW cruise system works so well, I can grab another brain at the junkyard for all of $5. Its a vacuum system and all, but who cares if vacuum servo or electric motor is pulling the throttle linkage? Its just 12v DC outputs.

Anyone had any luck with retrofitting a cruise amp from another type of car to your benz? If so, what make and model? I hate the fact that the VW cruise has no decel feature. So Im thinking Mazda - 1992 MX6 (most reliable car ever built, just fugly as hell).

One more question - the speed wire input to amp - should that be read in AC voltage, or frequency?

Tell me im crazy...and I'll post a pic of the interior of my 87 300D. You guys are gonna have a laugh. Just need the digital year read out and some plutonium.

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Paul
Benz-less
I need an SDL !

bump!

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Paul
Benz-less
I need an SDL !