Climate Control Fix?

[lakeside]

I guess climate control problems are common and I've serched for a solution to mine without luck, so far. My car: '87, 560 sl, with about 184,000 miles, and in fairly good condition. Here's what the climate control is doing or not doing. The automatic control doesn't work. It cools, then stops cooling and may start again after I turn the it off and back on. The auto fan control does not work so I have the fan on full. The heater works but the temp is not controlled. I get lots of very hot air. So, the temperature control wheel does not give sliding control but rather just cold or hot.

What should I look for?

[Kebowers]

A Japanese luxury car--they don't have all these flaws. Different Corporate culture--fin Japan, failure is shameful--to make a high-end car with defects would literally call for ritual suicide. Germany figure it proves your manly if you can keep their car running.

Not entirely a joke--unfortunately.

MBZ electrics are pre-WW-II caliber. OVP relay is common failure. The temp amplifier is another. etc.,etc.

[Roncallo]

Your problem is most likely cold soldering joints in the control unit (push button assembly). The Germans do not know how to solder. If you can follow wire diagrams and look at the board on the control unit you may be able to figure out which solderd joint is bad. There may be more than 1. Or else replace the control unit with a rebuilt unit. You may find articles on this repair pulished on the web or there may be an article in the DIY section right here.

John Roncallo

[tecqboy]

I strongly feel that when those Japanese cars get to be 20 years old they too will suffer from the forces of auto-deteriorization. Have you ever seen an '87 Lexus? Anyhow, solder joints do fail over time, particularly at points subject to movement. So, we often find that switches soldered to a circuit board need to be resoldered. The best approach is to use a solder removal device to get all the old solder off, then resolder with new solder. ( Tool = vacuum sucker or wick from Radio Shack). Solder is a mix of lead and tin and rosen. The rosen makes it flow better. Lead, tin, copper wire or brass switch contacts are dis-similiar metals and over time the connection breaks down. You can't blame Mercedes for a natural physical process.

From your description, I suspect your car has multiple problems which may includes sensors, heat (water) valve, vacuum motor(s) and other ACC parts. This is a very complex system and requires good diagnostic procedures.

[David Langsam]

I've nver seen an '87 Lexus! ....they were introduced in 1989.

[Roncallo]

Originally Posted by tecqboy

I strongly feel that when those Japanese cars get to be 20 years old they too will suffer from the forces of auto-deteriorization. Have you ever seen an '87 Lexus? Anyhow, solder joints do fail over time, particularly at points subject to movement. So, we often find that switches soldered to a circuit board need to be resoldered. The best approach is to use a solder removal device to get all the old solder off, then resolder with new solder. ( Tool = vacuum sucker or wick from Radio Shack). Solder is a mix of lead and tin and rosen. The rosen makes it flow better. Lead, tin, copper wire or brass switch contacts are dis-similiar metals and over time the connection breaks down. You can't blame Mercedes for a natural physical process.

From your description, I suspect your car has multiple problems which may includes sensors, heat (water) valve, vacuum motor(s) and other ACC parts. This is a very complex system and requires good diagnostic procedures.

I have no trouble blaming MB for this. Because non of this happened to any of my 3 Fords, any other car I owned.

John Roncallo

[lakeside]

John,
Thanks for the tips. I'll give resoldering a shot.
Jerry

[Kimo]

I had problems similar to what you describe with my '81 SL. I ended up installing a Unwired Tools ACC II Upgrade. I would not advise doing it yourself unless your experienced at doing stuff like this. I had it done. It was expensive but the system works very well.

[Strife]

What should I look for?

One of the first things I'd look for is the ignition switch (the electrical part). Jiggle the key and see if the blower turns on and off. This is not very expensive or difficult to fix.

[lakeside]

Originally Posted by Strife

One of the first things I'd look for is the ignition switch (the electrical part). Jiggle the key and see if the blower turns on and off. This is not very expensive or difficult to fix.

I'll the key-jiggle a try and let you know. I hopes it's that simple.

Jerry

[cbdo]

Fortunately, the ACC II upgrade doesn't (AFAIK) apply to your car; it's an issue with the previous system with the vertical pushbutton row, not with ours.

The ignition switch can indeed produce weird symptoms in the ACC, even when there's nothing else misbehaving. Mine had inexplicable assorted strange behaviors, particularly cutting in and out unpredictably, then gave a clearer clue when it would be dead at startup and cut in when I jiggled the key slightly. One new ignition switch later it's behaving normally.

A tip--You can keep the same keying by just replacing the switch unit itself and keeping the same key tumbler, IIRC. It's still a pain cuz the disassembly to do the job is surprisingly extensive, but at least you don't have to re-key anything to keep all the locks matching.

[Richard Wooldridge]

My theory about the solder problems (and there are a lot of them - problems, that is..) is that the Germans got on the lead-free solder kick long before we did, and the lead-free solder they use is far more susceptible to vibration caused failures than the good old 60/40 is. That's a very good reason to solder wick off as much solder as you can before resoldering. Solder failures just do not occur with a good solder joint. Tektronics, based in Beaverton, OR almost couldn't sell to government agencies way back when they started because the government wanted a mechanical joint first, then solder applied. Tektronics stuck to their guns - they used no mechanical connection, just solder, but used silver solder in a ceramic insulator. Lengthy testing proved their technique superior to the normal government spec, so they were granted license to sell... It's all in how it's done, and what you use to do it with. I think the wiring harness fiasco is another ecology-driven mistake that some bureaucrat in government dictated, thereby shooting him/herself in the foot, so to speak, as the result has certainly caused more ecological problems than it solved.
I suspect that most of your climate control problems will be solved by resoldering, as earlier suggested.

[Strife]

Originally Posted by Richard Wooldridge

My theory about the solder problems (and there are a lot of them - problems, that is..) is that the Germans got on the lead-free solder kick long before we did, and the lead-free solder they use is far more susceptible to vibration caused failures than the good old 60/40 is. I think the wiring harness fiasco is another ecology-driven mistake that some bureaucrat in government dictated, thereby shooting him/herself in the foot, so to speak, as the result has certainly caused more ecological problems than it solved.

I suspect that most of your climate control problems will be solved by resoldering, as earlier suggested.

Interesting comments...I wonder what will happen over the next few years with ROHS. Maybe lead-free solder joints are OK with surface mount parts, but through-hole...I don't know. Also definitely not helping MB electronics systems of that era is the use of phenolic circuit boards. In the US, toys, fer goodness sakes, were made with fiberglass PCB's starting in the late 70's. Using phenolic boards as fairly critical components in expensive cars without really extensive vibration analysis and support was pretty risky.

[lakeside]

I tried jiggling the ignition key and couldn't tell a change. Then I recalled that the previous owner had the ignition lock replaced. The mechanic that did the work also services my 520 SEL, and he said he had a heck of a time replacing the ignition lock on this SL. Is it possible that he jimmied something in the process or is there just one way the lock can be installed?

Also, it will be awhile before I tackle the resolding, in the mean time can anybody point me in the direction of a wiring diagram for the climate control on my "87, 560 SL? I looked in DIY, here and did a Google search but didn't come up a diagram.
Jerry

[deportes]

Japanese soldering sucks. If you ask anyone that has owned a Mazda RX7 from 86 to 90, you will find out that the Climate controller in all of them suffered from cold soldering issues. Lets get real with the german bashing.
Can't compare MB to any jap car.
Toyota MR2 have faulty windshield wiper controller/switch. And the similarities go on.