W124 slight issues
 

recently purchased a w124 300E in excellent condition. everything workin exceptionally except for three things.
1. cruise control. works sometimes, but then cuts out, or doesnt turn on.
2. a put a new stereo in, but cannot get it to function properly. it jitters when on CD, or radio. its as if it isnt getting sufficient power?
3. only the drivers side window works, the other three when operated short the circuit, cutting power to the engine.

seeing as all problems are electric, i wonder if they are linked? any information someone has on these problems would be much appreciated. thanks in advance! :)

(a) Cruise control. Unfortunately a hotbed of problems.
Known problems :
(1) Cruise control amplifier located under kick panel under steering column. Can develop solder breaks on circuit board. Solution is to clear off the lacquer coating from the circuit board with acetone (or finger nail cleaner) and resolder any suspicious looking joints.
(2) Hall effect sender on the back of the speedo.
(3) "Bouncy" speedo suspect speedo cable either kinked or not fed stright into instrument.
(4) Cruise control actuator - under the AFM in the engine bay. internal electrical problems.
(5) There is a small grommet on the accelerator controls that can go missing. The cruise actuator will not connect to the accelerator linkages smoothly.

New stereo. Do you have a fuse in the electrical live input? - maybe not connecting properly. Faulty earthing. If you install a modern head unit then you should run a new power supply.

Windows. Most likely one of the window switches in the console is giving a short circuit.

^ Usually the switches are fine...80% of the time the problem is that the wires that route through the door grommets can snagged and tear. When I got my 260E only 1/4 windows worked. All 3 that didn't work were due to torn wires. One of them was causing the fuse to blow each time the key was in ignition...but as they are fused in pairs, I had trouble figuring out why one window still wasn't working even after fixing the tear.

I had to run a power line directly to the battery with my stereo because the power to the stereo was AC and I needed DC. Correct me if I am wrong but could that be the stereo problem?
(I hope I am wrong because remembering to turn the radio off every time I get out of the car is a real PITA)

There is no AC in the car (except inside of the alternator). You were hooked to DC.

upon a bit of inspection, i found a wire running all the way under the drivers seat which had been shorting out wires surrounding it (due to faulty switch for power windows, thus heating and melting the wire)

so windows, are fixed.

now ill look at the cruise, but the stereo is a real mystery. i have a new power supply to it, and its a brand new pioneer head, with the original speakers.
it does the same thing with new speakers though, and the old head (orig) didnt do it at all.

on cds when the volume go's up, the quality drops more than significantly. just cant figure it out. its not the speakers or wiring etc.

thanks for the pointers though folks, i really appreciate it! :)

Have you installed new speakers with sufficient wattage and the correct ohm value to match you new head unit?

There is a volume balancing wheel in the centre console. Have you taken this out of the circuit? Newer head units have their own front/rear balacing and the need for this wheel is irrelevent.

Make sure you have the polarity correct between the speakers and head unit. I personally, would run new speaker cables.

I have a Pioneer headunit in my car- installed new power lead. I installed high quality Alpine speakers with new wiring. I left all the original wiring intact so as to re install the original becker and MB speakers when it comes time to sell the car.

well i figured it out! well not me, i went a radio guy (and he said the same thing as you as it appears!)
the little switch in the dash for the speaker allocation, was interferring with the output, apparently dragging it to earth!
still no cruise control though haha. i guess you cant have everything. if thats the only thing wrong with the car i can live.
where is the little accutator thing on the pedal though? i cant see anything so im thinking it may be missing :S
thanks a million for your help guys, its very valuable knowledge here! XD

my 260e did the same thing with the cruise control, until it finally just stopped working, didnt really drive it much after that (not for that reason)

but now starting to drive it again (sooooooo much nicer than my 2.0l 190e, that things bloody gutless, and it was a manual!), so, im looking at fixing this problem, going to look at the circuit board soon, ill let you know how i go

also my abs light likes coming on???
and my abs seems to be a 'little too good' at its job, like sometime i dont think its going to let me put the brakes on at all (when driving slowly) am i the only one that has this??