Cracked solder joints
 

What gives? Is this common in all modern autos? Is it not enough solder, or a basic faulty design? Do the re-soldered units become bullet proof or are newer units being made better?
I just went through this on the fuel pump relay and now my idle is up to 1500 (89- 300e) with no adjustment possible (I think) and I hesitate to just switch out the idle control unit thinking that it may just be getting bad data.
It seems half of the common problems with these cars -climate controller, OVP, and fuel pump relay, and others I don’t know of, are all cracked solder joints!
That’s a couple hundred worth of spares that need to be added to the norm stuff I carry in the trunk!
Is there a known culprit that puts stress to the entire system?

well, i think the fact that the car is approaching 19 years old might have something to do with it.

maybe engine vibration from worn motor mounts exasperates the problem

I hear ya, but these components have about as much total time on them as a 2yr. old television. I'm reading where these things can go out in a few months. I'm wondering if this is just common to the Merc's?

It's common in older 200 and 700/900 seriec Volvos too. The newer ones use a smaller realy.

It's common on ALL electronics components. :rolleyes:
Has nothing to do with any specific brand of anything.
Btw. unless you're talking about a " Mercury ", Mercedes cars are NOT " Mercs ".

If you keep your television outside in the winter, and twice a day get it up to operating temperature and let it cool off, I think you will find that you have trouble with its solder joints as well.

Of course, yours have only lasted this long because they used lead-bearing solder back then. Today's electronics are (mostly) lead-free.

Don't ignore vibration. These things take a pounding over time. The real problem is that they did not use "through plated holes" which are critical for reliability. Mostly because they used cheap single sided boards. There is no metal in the hole for the component lead and the heavier components are the ones that break first. Another 50 cents on the cost of the PCB and we would not be having this discussion. Double sided boards do not have these problems because the solder has two sides of the PCB to hang on to. If you cross section a double sided hole the solder looks like a double headed rivet. Much more solid than a thin layer of solder on one side only.

But then they would not get all our money buying replacements. Probably a good business decision for them.

The problem is a design defect, and although a common engineering error, it is preventable. This occurs when a relatively heavy electronic component is mounted such that the solder in the soldered connections is required to provide the mechanical mounting strength. A better design in THESE cases would be mounting hardware attaching the relays to the PCB's. A practical fix for the bad design is to 'suck' off the solder, wrap a smaller gauge solid wire around the terminal post, leaving the ends flush across to the solder pad surface. Trim and solder all. This returns some mechanical strength to the joint.

Steve

Have you verified that cracked solder joints are your problem? When I was having problems, I removed my relays and inspected them (based on suggestions from members here). I used a magnifying glass and looked over all the solder joints for small cracks. I did not see any, so I reinstalled the relays. After more troubleshooting, the problem was something entirely different. In my business, just changing parts at random is called 'shotgunning'. Change enough parts and maybe you'll catch the one that is bad. I would do more troubleshooting before replacing expensive relays.

You are exactly correct. However, the difference in cost is much less than 50 cents. More like 10 cents at those volumes for a small board like that. Hopefully they learned their lesson! The transition to SMT (surface mount technology) largely gets rid of the whole "hole" issue. If they would just make everything as good as their connectors then there wouldn't be any problems!

Interesting stuff. I can't remember if the older relays were rebuildable like these, but I do remember replacing some relay on a w108, 25yrs back. Certainly not the sophistication of one of these little guys.
I can understand that they could never sell the cars for what they'd need to with yesteryears quality, but little things like this, or the way the doors no longer have the safe like feel - weight I suppose - but I note they just have a cheap look. Whatever, it's a great car. Just not the light years ahead of everything else they were in the 60's.
Oh and "Manny", I've owned 5 Mercs over the last 35 yrs and none were made in the US or Canada:cool:

Wave Soldering
 

Basically EVERY Printed circuit board used in Automotive Electronics is Wave Soldered during assembly.

Do you think they do this in Stuttgart? Or Goteborg? or Torslanda?...

Try Matamoros, Calexico, Hermosillo. Try shaving pennies when subbing out the contracts to your suppliers and you gt Mexican Wave soldering and poor workmanship.

Bosch, Hella and AC/Delco all went to Mexico 20 years ago and all found out 3 year later they had assumed Detroit/Stuttgart/Torslanda levels of QA/QC existed in Mexico...they didn;t.

Get a 15 watt soldering iron and some basic lead free solder in 1/8th in diameter and open te relay or assembly and fix it in 10 sec by reheating the joint until the excess flux burns off and the solder flows well and let it cool.

Bob's your Uncle it works like a charm!

If you think that MB PCB's of the 80's are bad, you should see Becker stereo PCB's of the 1970's. Phenolic, or even worse. At least all the 1980's MB parts I've worked have had fiberglass boards.

Phenolic boards
 

Ever open a Sony PVM 8020 Video Monitor? Well the first thing you notice is all the "jumpers" all over the side bords done AT THE FACTORY to deal with the "peanut brittle" circuit boards (this was a Top of the Line 8 inch portable video monitor with all the same features as the VM1900 studio unit and retailed for close to $1500).

Becker? Try Clarion for brittle guts...we used to open the reman boxes and shake the new head units and if the sounded like a maracha we would toss 'em back in nthe box and try another one.

Hell I have a 1949 Motorola TV that is made better than 99% of the OEM non Delco based head units.

Now if you want to have fun, open a Blaupunkt and try an find a German part! Baseline Sony B Stock guts. But better than the crap I've seen in English cars...ChinoKorean sourced Euro units that cannot be fine tuned as there is no designed in potentiometer. If the factory effed up, that is how your freq's were set. My cousin says his Vauxhall sounded better with a wad of aluminum foil taped to the antenna cable connection and shorted against the radio chassi...no wonder all the really good "boffins" are from UK...they have to be to fix all the crap that is imported into the Empire.

John Lougie Baird is spinning in his grave as we speak!

Never mind.