Power door locks – The inside story

The adventure begins with wanting to install a keyless entry system into my '89 328. Since the car already has power door locks, how hard could it be? The bottom line is that it isn’t very hard at all. Of course you have to figure out how the locks work in the first place, and how they are wired up. Once you get through that, it is easy to install a keyless entry kit using the existing lock actuators in the doors. You don’t have to remove the door panels and the added components and wiring can easily be removed if you should want to later. You don’t have to take the door apart and you certainly don’t have to take the actuators apart, but I’ll show you how to in case you want to, or have to, at some point.

So I did a lot of hunting around to try and find out how the lock actuators worked but couldn’t find much info on them. I removed the fuse panel and started checking wires, using the factory wiring diagrams. My first mistake was assuming the colours of the wires would match the colours of the wiring diagram (note that I am Canadian and that is how we spell “colors” here.....see, you are learning another language at the same time!). OK, back to the wiring. There were some wires coming out of the door that did not line up with the colours identified in the wiring diagram, so I didn’t know which ones were from the lock actuator, which were from the windows, and which were from the mirror. I almost gave up at this point since I really didn’t want to take the door panels off. I thought I could hook up the keyless entry unit by just tapping into the wires behind the dash without going into the doors. I was right in the end. The door panels turned out to be very easy to remove. There is info on how to do it on the forum so I won’t repeat it here. The good thing is that there are no plastic fasteners that generally break when removing door panels; it is all just screwed together.

So for those that want to know more about how the lock actuators work, I’ll show you. With reference to the pictures at the end, the first one shows the door lock actuator installed in the door. Easy to see once you remove the door panel and any plastic sheet that is covering it. Trace the wiring to the front of the door and unplug it, remove the 2 mounting screws, and linkage that is clipped to the door manual lock above it. The unit comes out, and if yours is like mine it is sticky with undercoating stuff. Clean it off and take it to the bench.

There are 4 screws holding the case halves together. When you pull it apart you will most likely destroy the rubber sealing ring that goes around the perimeter; don’t worry about it, we’ll fix it later. As soon as you get it apart you’ll see why I call it an actuator, not a solenoid. You can see from the pictures that it is a small motor with a series of gears and a large rotating electrical contact. The rotating contact gear is what moves the actuator output arm. I took some pictures of it in both the locked and unlocked positions so I could better see how it worked by tracing the contact paths. Whoever came up with this was very clever, slightly insane, or a bit of both. I did find the word “Ford” on the electrical connector housing and I read somewhere that it was possibly used in a Granada. I also read that it was used in some Lotus’s, so it is not a specific Ferrari part.

One thing I was impressed with is how it looked inside. There was virtually no wear on anything, the grease was still like new, and it was very well designed. After spending some time with tracing the contact paths in the various positions, here is how it works. The red and brown wires carry power into the unit (positive and negative 12V obviously). The yellow and white wires just run from one unit to the other unit (in the other door). So when you lock or unlock one door, the yellow or white wire provides the signal to the other door to move to the same position. These wires are negative when being actuated. So what it boils down to is this; hook up +ve and –ve to the red and brown leads. Then put a –ve current into the white wire to unlock the unit, or a –ve current into the yellow wire to lock the unit. This is simulating the -ve coming from the other unit. Once it is actuated the –ve lead doesn’t do anything. What I mean is that when you put –ve on the white wire the unit goes to the unlock position. Putting –ve on the wihite wire again doesn’t do anything. If you trace the contact patterns you will see how this all works. So what this means, in theory, is that hooking up a keyless entry system should be very easy. Put a negative current on the white wire (running from door-to-door) and the doors both unlock. Put the negative on the yellow wire and the doors lock. It is actually that easy, other than the fact that the wires change colour when they go from the actuator in the door to the harness that exits the door, so you won’t find a white and yellow in the car; if you do, they are not the proper door lock wires.

Putting the actuator back together is fairly easy. Use the pictures to align the main contact gear with the output arm (in the locked or unlocked position). If you don’t get it dead-on it’s OK, it will align when you power it up. Since I didn’t have a replacement seal for the casing (who in the world would?), I put a small bead of RTV instead. Actually what I used was “Goop” which is similar but maybe a little more versatile. You could probably find a length of sealing rubber to use if you really wanted to. I wasn’t worried about taking it apart again. In fact, the unit looks very well made and I can’t really see what could go wrong with it. I suppose if the door lock jams maybe the gears could strip? More likely burn out the motor. Or a wire within the unit could break. Anyways, if you want to take it apart to investigate now you know how.

Oh, the colours of the wiring. The white wire from the actuator ends up being the black/white wire that runs from one unit to the other under the dash. The yellow wire is the blue/red one (be careful with this colour as it is the dark blue, not the light blue, and the red looks sort of brownish – compare with other wires in the same bundle to sort it out).

So now you know and you can say “very interesting, hope I never need to know this”. I’ll post another thread on how to hook up a keyless entry system, but you can likely figure it out by now.

Fun stuff this wiring!

Rick
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No guarantee that I can fix it, but I can certainly give it a shot. And the price will be right too!

PM sent.

Rick