Over the past while I've been having what seems to be a very common problem with my door locks: Intermittent operation. My symptoms were:
Since we had some lovely weather over the weekend, I took the opportunity to strip all my doors, removing the locking mechanisms and disassembling them to see if I could sort out the problems. Given these modules are around £120 each, it was worth a shot!
Each module was removed and bench tested so I could see what was happening. In all cases it appeared the motor was struggling slightly to flick the mechanism over. On the three mechanisms that were giving trouble, it seemed that the motor wouldn't even bother trying in some cases (the rear door module was stuck in this state). There was no power draw which indicated that the mechanism wasn't jammed solid, so I took the modules apart.
Separating the mechanical lock section from the electromechanical section is relatively straightforward. The lever connected to the internal opening handle needs to be pulled past its normal opening position, and the T8 Torx underneath the body needs to be removed. Two small clips and a large tensioning spring then hold the parts together. Once separated, the wires to a microswitch still join the two sections so be careful.
Only one module had the fault that's frequently suggested - the driver's door PCB had some cracked solder joints, which explains the intermittent operation of both the motor and the courtesy light. With these joints repaired however there were still "dead spots" in the mechanism - some positions where it wouldn't even try. This pointed to the motor itself, as it did in all 3 troublesome locks.
The motor itself looks fairly standard but I couldn't find an online source for it, so I had a go at disassembling it. Motors are simple devices really, but are precisely manufactured and are quite delicate internally so be super careful if you're doing this! Removing the motor from the lock mechanism meant simply holding the metal power connections in place with a screwdriver and gently pulling the motor body away. The power connections simply pull out of small slots in the motor's body, and then the motor can be disassembled.
Inside, the commutator was totally caked in carbon from the brushes. I cleaned it all up, flattened the edges on the brushes slightly with a tiny screwdriver, and reassembled and tested. The motor now worked fine with no dead spots and consistent torque.
Before reassembling the mechanism I took apart the rest of the gearing and levers associated with the motor, cleaned and greased them with special plastic-safe grease normally used for industrial printers. After assembly I tested the mechanism and it no longer needed any help switching over, regardless of where the motor was stopped. New grease was put in the mechanical portion and the whole lot was put back together in the door. The same was repeated for all 4 locks, and testing found that they were now working 100% of the time via the key fob. Result!
What I learned:
The only problem I now have is that one of my doors only opens from the outside the second time I pull the handle after unlocking. Similar to opening the doors from inside when they've been locked with the driver's door control, but on the outside. This shouldn't happen so I'll probably take that one apart again and see what's wrong. Might also take some photos of that since I neglected to do that the first time around.
I can put more details up if anyone needs them - turns out I'm very familiar with the workings of these modules now!
- Driver's door sometimes not opening via key fob
- Courtesy light sometimes not working for driver's door (and so fuel pump not always priming)
- Front passenger door not opening via key fob most of the time, though you could hear it trying
- Rear left door not locking, not even trying
Since we had some lovely weather over the weekend, I took the opportunity to strip all my doors, removing the locking mechanisms and disassembling them to see if I could sort out the problems. Given these modules are around £120 each, it was worth a shot!
Each module was removed and bench tested so I could see what was happening. In all cases it appeared the motor was struggling slightly to flick the mechanism over. On the three mechanisms that were giving trouble, it seemed that the motor wouldn't even bother trying in some cases (the rear door module was stuck in this state). There was no power draw which indicated that the mechanism wasn't jammed solid, so I took the modules apart.
Separating the mechanical lock section from the electromechanical section is relatively straightforward. The lever connected to the internal opening handle needs to be pulled past its normal opening position, and the T8 Torx underneath the body needs to be removed. Two small clips and a large tensioning spring then hold the parts together. Once separated, the wires to a microswitch still join the two sections so be careful.
Only one module had the fault that's frequently suggested - the driver's door PCB had some cracked solder joints, which explains the intermittent operation of both the motor and the courtesy light. With these joints repaired however there were still "dead spots" in the mechanism - some positions where it wouldn't even try. This pointed to the motor itself, as it did in all 3 troublesome locks.
The motor itself looks fairly standard but I couldn't find an online source for it, so I had a go at disassembling it. Motors are simple devices really, but are precisely manufactured and are quite delicate internally so be super careful if you're doing this! Removing the motor from the lock mechanism meant simply holding the metal power connections in place with a screwdriver and gently pulling the motor body away. The power connections simply pull out of small slots in the motor's body, and then the motor can be disassembled.
Inside, the commutator was totally caked in carbon from the brushes. I cleaned it all up, flattened the edges on the brushes slightly with a tiny screwdriver, and reassembled and tested. The motor now worked fine with no dead spots and consistent torque.
Before reassembling the mechanism I took apart the rest of the gearing and levers associated with the motor, cleaned and greased them with special plastic-safe grease normally used for industrial printers. After assembly I tested the mechanism and it no longer needed any help switching over, regardless of where the motor was stopped. New grease was put in the mechanical portion and the whole lot was put back together in the door. The same was repeated for all 4 locks, and testing found that they were now working 100% of the time via the key fob. Result!
What I learned:
- Worn motors appears to be a common fault for these modules, affecting 3 modules on my car
- Only one module had poor solder connections
- Every microswitch in every module was working perfectly
The only problem I now have is that one of my doors only opens from the outside the second time I pull the handle after unlocking. Similar to opening the doors from inside when they've been locked with the driver's door control, but on the outside. This shouldn't happen so I'll probably take that one apart again and see what's wrong. Might also take some photos of that since I neglected to do that the first time around.
I can put more details up if anyone needs them - turns out I'm very familiar with the workings of these modules now!
