Installed a keyless remote entry to my 83 300D
 

Installed a keyless remote car alarm to my 83 300D. I am amazed on my well it works on a 26 year old car. This is what I did:

1) Fix all the doors vacuum actuators, make sure I can central locked everything.
2) Installed an actuator on the driver's door to control the vacuum switch.
3) Hook up all wires to left/right running lights.
4) Hook up door wire to driver's door only. I cannot find a signal for all the doors open/close signal.
5) did not bother with starter kill relay.

The central lock will operate approx 10 times until the vacuum tank is exhausted.

Question: Anyone can advise on how to hook up door signal centrally without using diodes to combine signals?

I don't understand your question. If you have the electric actuator connected to the driver's lock mechanism, all doors should lock/unlock together...like it did before.

The control unit needs a signal to indicate door open/close. It is also used to detect break in. I can only connect to the driver's front door, not the rest. There is no signals that I can tap into to indicate any doors is opened. That is if someone breaks in through the rear door then the alarm will not go off.

I can connect to the other 3 doors by running wires and using diodes to combine the 4 wires but it is too messy and I do not want to do it. It works good now except of the short-coming I mentioned above.

ah, gotcha. Could you simply tie into the front and rear overhead lights?

Running wire to the overhead lights is possible if I can identify the wiring underneath the dash. Then it is only combining 2 wires. Will try to look at the schematic.

The dome lights.