Problems fitting new alarm

[KLP 92]

I'm currently installing a new alarm on my 500sl 82 model.
I've run into one problem, that is the remote central locking. On close examination it appears my system runs on a vaccuum system. Where do i connect the alarm wires into? Is there anywhere that controls the vaccuum pump that i could connect up to?

 

[Richard.Wilson]

Hi there,
I cannot speak from experience, of fitting an alarm to the circuit, but I've messed with the locking on my W124. Looking at the circuit diagram, it appears that the only inputs which control the vacuum unit are connected to the following:-
RH door actuator,
LH door actuator,
or Luggage compartment actuator
These are connected to the Vacuum control unit (green yellow and blue wires on W124). There is also a common connection of these to the unit with a white wire.
I guess the logic is that white wire controls "lock" and any of the three colours would control "unlock" or visa-versa.
That seems to be the only input to the control unit......
Hope this helps.
Richard

 

[talbir]

The center-point vacuum locking system on the 124/126 etc is operated by one common vacuum pipe and one common wire at the pump, which is blue in colour.

The blue wire when earthed locks the doors and trunk and the same wire when supplied +12V unlocks the door. A minimum 3-second pulse is required to complete the operation, i.e. ground must be supplied to blue wire for 3 seconds to enable pump to lock the doors and +12V for 3 secs to the same wire to unlock the doors.

You may need an additional module to perform this 3-second pulse feature (it is basically 2 SPDT relays wired in a certain way with 2 pulse timer relays in line for the 3-second pulse).

If you are in luck, your alarm brain may have this pulse feature built in for vacuum controlled locking systems. This should be explained in the alarm installation instructions, on how to program this feature up.

Let us know if you need anymore help.

 

[KLP 92]

Thanks Mr Bains for your advice.
I will let you know after the weekend how its going.
Nice car by the way, saw it in Mercedes Enthusiast.
I'm currently working on my 500sl and was wandering who did you use to carry out your work?
I used the same guys you did for your exhaust as they remembered doing your car!

 

[liverpooluk]

I got a cobra Thacham Cat 1 fitted to my '92 300D

First they quoted £300, then realised the vac system employed on the motor.

Ended up paying £350. :evil:

Well worth it though. The only time i use my key now is to start the engine and to deadlock the boot! :lol: :lol:

Remote Central Locking works about 30ft away. Nice way to show off i suppose!