Central Locking Diagnostic

[tdoyle]

Hi, Ok then. I'll see what it looks like when I get it apart.
Thanks for the help.
Tim

[StereoInstaller1]

An E30 in the states without central locking is a very rare bird.

[tdoyle]

Stereoinstaller,
Thanks for the info. I will open it up after the holidays. Is it assumed that the car has power locks? Or can I confirm by looking for a fuse/relay?
Happy Holidays,
Tim

[StereoInstaller1]

BTW, I wanna thank Tim for asking a question intelligently, including vehicle info.

Thanks!

Luke
9reserved for future crap)

[StereoInstaller1]

I got a PM this morning and I though I would share the answer with R3V as I get these questions pretty often:

i have a 92 318ic. (build 4/92) drivers door will open with the key, but will not unlock, although the key turns in the cylinder. If I unlock the passenger door with the key, it has no effect on the drivers door. I am not sure if there are power locks, or just manual.
Any ideas/
Thanks,
Tim Doyle
ps, followed your instructions for radio install in another thread. worked perfect!

Tim, here is a basic idea of how our power lock system works:

There are 5 wires to each "active" door lock "actuator" or solenoid. 2 run the motor, 1 is ground, and the other 2 instruct the central locking module to either lock or unlock.

When the actuator moves, one of those request wires will go to ground...kinda makes sense, right?

So: white and blue are the motor wires
Brown is the ground
Yellow/blue is lock request
Green blue is unlock request

These might change as they go into the door, that is not my responsibility! Read your ETM or electrical diagram carefully.

Motor wires: Both white and blue will show ground when the system is at rest. One of the 2 will switch to ground when the system is attempting either lock or unlock, so the motor gets both +12V and ground...if the system requests unlock, the other wire goes to +, see?

This is called "voltage reversal", and is used pretty much any time a motor is used in 2 directions (i.e., not the HVAC blower motor, but windows, etc.)

So a basic test is to remove the plug from the bottom of the door lock actuator, make a small jumper to quickly and briefly connect from the ground to the lock request wire and see what happens.

Once you actually get off your butt and take the door apart this will make more sense.

Keep in mind that if you are doing this in the drivers door you must "fake" the lock system into thinking the door is closed, so flip that latch before any testing.

So, if you can lock and unlock the car by jumping the wires, your actuator is crapped out.

Simple, huh?

Other issues in the central locking system will be addressed later

GL!
Luke