Just done my 740 but with a non-Volvo lock motor.
Your sytsem`s existing door switch is a negative pulse system.
It grounds one wire with the key turned clockwise and the other on turning it the other way. This triggers the existing c/locking relay to send a pulse down the two lock motor wires which go to all the lock motors to lock the doors.
When the opposite ground is made by the door switch the relay sends another pulse with reverse polarity to the motors to unlock.
I too suggest that you keep the existing relay and use the new system to trigger that.
Your "new" motor wires then just splice into the wires going to any of the existing motors,and those from the remote to the switch wires.
If you can`t figure it out, e-mail me a copy of your remote kit`s instructions
and I`ll try to sort it out.
Colin.

I did the same thing you are on my 740. Do not just use the wires from the alarm straight to the motor. They are probably not designed to power the motor. I had two wires like you described, and a third +12v source from the alarm. I used the +12v to power the relays and door lock motor and eventually it blew the circuit (took a week or two). I'd recommend to only power relays with the two wires you have for your alarm and borrow +12v from somewhere else like the ignition harness... (that's what I did, other's might say that's a bad idea, not sure)

-Nathan

Is the locking motor a two wire motor or a five wire motor?
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George Holmer, Belgium, Europe, 1987 745 GLE Turbo Diesel Intercooler (D24TIC/M46) 200k; 1988 745 Turbo Intercooler (B230FT/M46) 290k; 1988 745 GL (B200E/M47) 190k

Good day. I have installed a cheapie door lock/unlock system in my 760. I used the motor and linkage from a 1986 740.

To determine how the wires are connected, you'll need to figure out what kind of outputs they are. There are "negative outputs" and "positive outputs". If the manual doesn't say anything about this, you'll need a multimeter and a 12v power supply.

If you are familliar with electronics or computers, negative output is synonomous with "open collector". This means that the wire is usually open, not connected. When the wire fires, it becomes a ground or chassis connection, draining a 12v source. The problem with these is that they usually won't take much current, and are nevertheless worthless for direct connection to the motor.

If the outputs are positive, see if the outputs ground when they arn't on. If they do, you can connect the lock and unlock streight to the motor.

My installation used negative outputs. I constructed a circuit board with relays that connected it to the motor. Mine also has a relay in the door so I didn't have to run a relay across the hinge.

If you're near the Northwest Arkansas reigon, I'd be more than glad to demonstrate and/or assist. If not, I can draw you schematics of what you'll need to get the desired effect.

Good luck!
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89 764 GLE 150k/ 86 745 GLE 240k