Internal door lock switch

[steveb]

Does anyone know a model which has a door lock switch on the console - I have a SEC which I would like to fit a switch which looks as if it were original equip.

Also does anyone know where to link in wiring (or where to find info)

Ta

Steve

 

[talbir]

Hi Steve

I have fitted the original MB door lock switch in both my SEC's and my SE. It's a wonder why MB never fitted these in the first place - it's so inconvenient without the switch.

MB made two types of door lock switch - one with an LED and one without. Part numbers are 124 821 50 51 and 202 820 40 10 respectively.

These switches were fitted to MB's late 90's, so the 126's don't have them.

These switches only fit into the coin tray on 126's - they are the type that slot in from underneath.

To fit the switch, you need two SPDT relays and two timer-delay relays. The timer delay relays are required, since the vacuum pump requires a 3-second pulse to trigger locking/unlocking. If you don't fit the timer relays, you'll have to hold the switch down for 3 seconds each time - not very convenient. The central locking on the 126 is controlled by one wire, which when grounded locks, and with +12V unlocks. Therefore you need the relays type circuit, to keep a continuous circuit for the alarm or door locking with key etc.

The only wiring you need to do is feed into the blue lock wire which runs from driver's door to vacuum pump and the grey/blue illumination distribution point, so that the switch illuminates when you turn your lights on at night.

It's a great addition, but does require a little effort.

Let me know if you require wiring diagrams, or further assistance.

cheers

 

[steveb]

Thanks for info.

When you say coin tray, do you mean depression in plastic in front of gearshift - & how does the switch then mount?

I am going to see if I can find the door lock unit for the alarm fitted, as I may be able to 'spoof' the alarm lock/unlock signal & that should give me the delay I need.

Any info about one-touch window lifts?

Steve

 

[talbir]

Hi Steve,

I have developed a unit which works with my lock switch - basically you can lock/unlock the doors from the switch anytime you choose, regardless of whether key is in ignition or not. Also, more importantly, if you forget to lock the doors, they will AUTOMATICALLY lock once a speed of 8mph is reached. This is on all of my W126's (560SEC, 500SEC and 300SE). So it works just like the late MB's and is very cool !

I also have 1-touch windows all round in all 3 W126's. However, this really requires aftermarket modules. You could do it yourself with relays, but to prevent damage to the window motors, you need resistor relays, which recognise when the window is fully open/closed. Also it is much neater with a purpose-built module. They are about £50 each (which covers 2 windows). The rear windows are a little more tricky to wire up as they have to be one at the rear window motors. The fronts are very easy, simple wiring under the centre console switches.

The coin tray is exactly the piece you describe - there are two types. One which just has a single large well for coins etc and the other has a smaller depression and a row of switches along the top (depending on how many options your car has).

Your car is a 560 ? So you should have the later type coin tray, which although may not have any switches in it at current (or may have the heated seat switches, dual horn control etc if you have these options), the coin tray always has the facility to add switches to it. The back of the tray has a plastic panel with 5 slots - the coin tray can be simply cut (using the right tool) to slot size to enable another switch to be hooked up.


Yes, you could wire up to the alarm - although this will alternatively mean that you will need a latching relay set-up to give a constant signal. The MB door lock switch is only a momentary contact switch (like your heated rear windscreen switch) and the alarm brain will require a constant ground to trigger the door locking sequence. Therefore you will need either a latching relay or just use 2 SPDT relays wired up in a certain sequence to form a latching relay.

Some alarms have the option which locks doors on start-up - this works when a +12V signal is received by the alarm unit. So in this case you simply need a set of latching relays to send a constant +12V when you press the switch once.

Bear in mind, you also need another relay, which is triggered by the door pin switch, so that anytime the door is opened, the latching relays are unlatched. Otherwise, if you exit the car and enter again, you will have to press the switch to unlock and then press to lock to lock the doors.


cheers

 

[steveb]

That sounds a nifty lock mod Talbir - do you have details?

Also what other mods have you found to be useful?

Steve