Vacuum solution?

[Hemersam]

The windows on my '78 280SE are driving me crazy; some lock/unlock, some don't, all decide on how they feel about the question at the moment!  I'm sick of them and want to disconnect the vauum lock system, period, and just use the ignition key to open and close the front doors. I'm told I can do that but have to "plug" the vacuum line which comes out of the manifold to operate all this "suuff."  Question: where is this outlet and with what do I "plug" it?  I'd appreciate some pictures if possible (the "picture worth a thousand words thing"!!!). Most grateful!
Hemersam

[pez]

Your windows are electric. Your door locks are vacuum.  They are not hard to diagnose and fix - it just takes a cheap hand vacuum pump and the ability to remove door panels. If you are really wanting to not have vacuum lock operation, then plug the yellow feed line. You can do most simply at the firewall on the drivers side [LHD].  But I would urge you to take the slightly harder route and get things working correctly for the sake of the car!  When you are in the doors, the main yellow line goes to the vacuum switch on the drivers door, the yellow/red locks, and the yellow/green unlocks.

[Hemersam]

     Oops, I bungled the first sentance of my thread; I meant to write that I was sick of my 280SE non-functioning locks (not windows). Anyway, thanks, PEZ, for pointing out where I could plug the vacuum line and just use the key to lock/unlock the front doors. I'm the only person who ever drives my beauty, beside the fact that I'm 73 now and not as eager to get into door panel removals, etc. Maybe next Spring. Thanks again.
Hemersam

[WGB]

You will probably have a ruptured diaphragm in one lock which will stop the whole system from working.

It is worth fixing.

Link to purchasing separate diaphragms

Thye vacuum diagram for how it all works can be found in the workshop manual.

Very simple to work on - if too hard suggest you pay an M-B specialist.

Bill

[virtualgarage]

You may also check the switch for that window. Gently pull out the switch with a flat screwdriver. Peel off the cover of switch carefully. Clean with WD40 and put everything back in order. It doesn't take you lots of muscle but does need your concentration since the rock metal plate inside the switch does need your attention.

Swap with another window switch isn't recommended since all switches are clogged after these years. The lubricant inside these switches are drying out is the main reason causing this weird window.

A small flat screwdriver to pull the switch out and open the cover, a tweezers to pick small rock metal plate up and put in order and WD40 are all you need.  Maybe another good glasses

Another easier way is eBay. Find a good switch and replace.

HTH

Rocky
'78 6.9
'69 6.3
'57 220S

[BAR]

Given that your windows are working and that you have clarified the situation: so your door locks aren't working.

As has been explained, the whole central locking system is pneumatic.  The pressure / vacuum is created when the motor is running and there is a 'storage tank' in the boot above the fuel tank.

Generally failure to operate, when the vehicle has been parked and engine off after some time, is caused by a leak in the system.  All locks are operated individually by a 'bellows': there are separate units in each door and the boot [for the boot lock and fuel filler door].

Most faults are caused by cracks in the rubber bellows: one can replace the whole unit or if careful, buying one complete unit can provide 4 rubber bellows [ I haven't found out where to buy just the rubber as this is what fails and not the rest of the assembly].  Occasionally the vacuum lines, being hard plastic, crack and allow leaks.  These can be 'patched' by using silicone hose to rejoin the line after making a clean cut through it.  This silicone hose can be bought in most tune up shops for a few dollars per metre [or yard for the non metric folks].

One needs to have a quiet environment and run the motor for a while to pressureise the system and then shut off the motor and move around inside the vehicle to listen for a whistling noise that would be the giveaway for a leak.

Again, the common faults are either a failed rubber diagphragm in the door locking bellows, or a cracked vacuum line - usually close to where the lines pass from the body work into the doors.

Once the source is identified, carry out the appropriate patch.

[CraigS]

This is probably the easiest way to go.

http://mercedessource.com/node/1044

http://mercedessource.com/node/1050

[Hemersam]

  I very much appreciate the replies you guys have given on my door lock miseries; you've given me some clues about what to do. One last question (I hope): once I've driven the car a good distance, say 10 miles or more, the door locks will usually go down when I lock the driver's door---EXCEPT the rear passenger door; it NEVER does anything, NEVER.  Is this "proof" that the problem is in the mechanism of that door?  Thanks so much.
Hemersam   

[oscar]

It's as good as definitive proof that's the problem door and it would be the first door I'd take apart.   Replacing the part/s in that door, either the diaphragms or the vacuum unit as one, should cure your problem though it's likely that there may be other leaks.  After attending to this door, if your system holds a vacuum and can operate the locks after the car has been sitting overnight I wouldn't bother looking for other leaks.  I've been slack chasing my leak/s up due to other priorities but mine holds a vacuum for about 2-3 hours.

If you need advice on door trim removal there's a few pics here - Link

[WGB]

The big trick with removing the door trims aftger removing all the screwed on hardware is to lift them vertically - parallell to the vertical plane of the door - and then pull them off.

Unlike every other car ever made they have fragile hooked plastic fittings that need to be disengaged vertically before removal although it is likely that if anyone clumsy has got there before you they will already be broken.

Bill

[koan]

Unlike every other car ever made they have fragile hooked plastic fittings that need to be disengaged vertically before removal

Hmm, yes, I managed to break a couple of the hooks off, the trims can be a bit stubborn where they clip on at the top.

I bought an old door trim, cut the good hooks out and cut matching holes into my existing trim. With a soldering iron and some extra plastic bits from the old trim I was able to plastic weld the hooks back on.

koan