Help fitting alarm (central locking bit) W124

[doshbass]

Dear All,

Can anyone give me a rundown on how to trigger the central locking from my Alarm system.

So far I have managed to get it all working, inluding remote start, but the CL is really getting to me.

The alarm has a number of modes, however all of them do similar things, basically I have a pair of wires, or two pairs of wires that have full continuity between them, until you either arm or disarm the alarm. At that point the continuityy between the wires breaks for just under 1 second and then rejoind again.

As I said, I can either have one pair of wires that will pulse for both lock and unlock, or 1 pair that pulses on unlock, the other pair will pulse on lock.

I have tried to make this functionality work from the drivers switch wires, but this just doesn't seem to be the way.

So If anyone can give me an idea of what I can do, or at least how the central locking can be triggered, I would be very grateful.

Jon

 

[television]

Without a long serch, the normal locking and unlocking is done with the air pump,,in one mode it locks (blows) and in the other it sucks to unlock, so all that happens with the MB central locking is that the pump runs for a few seconds.

With a pulsed circuit you may have to put a relay into the circuit to give the momentery contact needed as the pump cannot run all of the time.

Malcolm

 

[aaron6155]

the car has a vacuum pump under the right hand rear seat, there will be a 3 pin plug on it with a "yellow a green and a blue wire" these come from the three locks , yellow is boot, etc, now these work as "earth to lock and positive to unlock" you can use either of these 3 wires to trigger the locking pump as long as you can get your alarm to give these signals on arm and disarm, it does not have to be timed pulses just straight forward earth and positive signals.
Hope this helps.

 

[turnipsock]

There is one wire from each of the three locks on the car.

When you turn the key, a wire gets grounded, or to 12V, briefly. This starts the pump running for a short period, enough to open or close all the locks.

I have a problem with my drivers door not activating the central locking. After checking things out, there isn't a full 12V on that door. I also get the same voltage on the alarm that has been fitted at some point. I can open the CL from the drivers door, but not lock it from this door.

I guess whoever has fitted the alarm has spliced into the wire running to the drivers door to activate the CL.

 

[Thegemmesabogie]

I fitted my alarm recently so can only advise on what I did. The alarm has one pair of wires. These were soldered in series with the green wire from the passenger door to the pump. Polarity is not important. The alarm instructions say that for Merc the pulse switch on the alarm should be set to 6/25secs, i.e. long pulse, which may be the important point for yourself.

 

[doshbass]

Thanks for the advise all, I did splice the wires in the door, but to no avail. Interesting that it needs such a long pulse.

I actually have 6 wires going to the pump 2 of each colour. Does anyone know why that may be and does that make a diference?

Jon

 

[doshbass]

New information,

The wires in the door as far as I can tell are blue/white tracer, brown and red/white tracer.

The Red/w wire seems to have permanent 12V, The brown seems to be permanant earth. The blue/w has 12 volt on lock and nothing/earth on unlock, however when I apply either earth or 12v to this wire nothing happens.

The CL works fine on the car.

So that seems to wipe out the applying 12v or earth theory, unless there is some difference between doing it at the pump end, to the door end.

Regarding the Pulse, The alarm can be set in normally open circuit or normally closed, however if I manually disconnect and reconnect the wires, I still get no reaction from the CL, so I can't see how this pulse thing will work either.

This is really driving me mad, it can't be that difficult, now the autostart mechanism was a real mystery and I needed to rewire the alarm and put in an additional relay, but the CL should be reletively simple.

I am open to, and eager for, any and all further suggestions

Jon

 

[turnipsock]

Even though you have six wires, is it still a three pin plug on the pump?

I would rig up some bulbs (LEDS would be better) to see what is happening. That put one between the feed wire and the 12V and one between the feed wire and 0V.

You can then turn the key to see what happens.

 

[doshbass]

Thanks Turnipsock,

Will do this and report back

Jon

 

[doshbass]

Almost there now

Thanks again Turnipsock,

I chos one of the 6 wires in th eback and tested, 12v+ on unlock and earth on lock.

By splicing in a wire, I could then unlock by toching the wire to 1 12 volt feed and lock by earthing the same wire. Great I though now were cooking on gas, however the alarm system doesn't want to play nice. I have got a flash of 12 volt and a flash of ground when I lock and unlock, but it seems th epulse is not long enough. It works fine on unlock, but wiull not lock again.

So now I am looking, as you said, at a relay, but what kind of relay. Given that my pulse is less than a second, I need a relay that will switch ans hold until reversed, is there such a thing?

To sum up, I now have two circuits, on lock one will briefly power, on unlock the other will so a switching relay that will take two circuits in and allow a feed wire to swap output (or actually input inthis case) from two terminals,

Can anyone identify that little beastie.

Jon

 

[doshbass]

Damn,

I just realised this wont work, or at least would work, but if I tried to unlock the door manually, either, in the worst case, I would set fire to the car, or ,in the best case, it would simply relock itself immediately.

So now I am thinking about a couple of single shot 3 second delay timer relays

This is not the most fun I have ever had.

Jon

 

[television]

Damn,

I just realised this wont work, or at least would work, but if I tried to unlock the door manually, either, in the worst case, I would set fire to the car, or ,in the best case, it would simply relock itself immediately.

So now I am thinking about a couple of single shot 3 second delay timer relays

This is not the most fun I have ever had.

Jon

Your cheapest way for a delay is to add a diode over the relay, that will give 2 sec+ put a cap you can get up to 4 sec with no problem.

malcolm