Hi everyone,

I bought an '89 560SEL (my first M-B) in September and have been using it rather heavily (I've put 8,000 miles on it since), and enjoying it tremendously. It does have a few nagging problems, though, and I'd greatly appreciate any/all tips before I tackle any of these problems with my hands and/or wallet....

1) The driver's side door doesn't trigger the courtesy lights and alarm; the other doors do. A search through previous posts on this site revealed that this may be a relay problem -- can someone please elaborate, since I'm a little illiterate when it comes to M-B electonics? Is this a DIY fix? What do I need to do?

2) The AUTO setting on my A/C unit works only intermittently; the slow and fast fan settings work fine (except for one morning, when none of the buttons worked). The car also makes long "sniffing" sounding noises when the A/C is on (especially if the car shifts its weight, as during braking or acceleration), and there are occasional popping sounds coming from somewhere in the front as well. Are these noises normal? What's the most common cause for the AUTO setting malfunction (other than a faulty button, which I doubt)?

Speaking of bezerk electronics, I've had one episode in which my A/C unit shut off completely, and, at the same time, my turn signals didn't function either. Then after a few minutes the air suddenly came back on and the turn signals started working again, too. Another time, at night, all the lighted buttons on my A/C unit went dark (but it kept blowing air, and all the other buttons stayed lit). It stayed like that until I stopped for gas; when I turned the engine back on, the lights were back, too. Could there be some common cause for all this weirdness? Bad fuses? Bad relay?

3) The car idles rough for about 5 seconds after start-up, usually when it's cold outside, then runs fine. Is this usually a dirty injector? Can I just add some STP Fuel System Cleaner, or do I need to have this professionally taken care of?

4) Most annoying: car starts vibrating around 70mph, then gets variably better or worse as I increase speed; the severity of the vibration and whether it gets better or stronger with speed varies randomly. Balancing (by two different shops), alignment, and tire rotation didn't help. There's also some balding on the outside of the left front tire. The left outer tie rod was recently replaced, without any benefit. The right control arm was replaced a few years ago. I know numerous other owners have had problems like this, and often they can't find the source of the problem -- having said that, though, what should I have checked/replaced before I give up?

5) The car has 136k miles on it, and I guess that means it's due for a guide rail replacement. I understand that the guide rails can break and the plastic debris as well as the off-track timing chain slapping around the engine bay can cause lots of damage. What I'm not clear on is this: do the rails break because they are old and brittle, or do they break if/when the pretensioner dies and the chain gets slack (and slaps against the rails with more force than usual on start-up)? IOW, am I better off replacing the rails, or the pretensioner, or both?

I realize this was a really long post -- thanks in advance for reading this far and taking the time to share your knowledge with me. I look forward to your replies!

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Janos
1989 560SEL
1993 400E
1994 E320 wagon