Over the last week, I've read or at least skimmed every post in this monstrous thread. Here's a quick summary with a focus on microswitch selection.
The most common lock module failure is the microswitch that detects whether the door is latched or not. The original design uses a pin-type switch which rides the outer edge of the latch itself -- the part that rotates to secure or release the post affixed to the door frame. The latch is steel, but it is clad in a somewhat soft plastic -- HDPE, probably. Over time, the pin on the microswitch digs a hole in the plastic where it rides, and then the hole catches the side of the switch pin and rips it off. This destroys the switch function and usually rips the pin seal as well, allowing dirt and water to get into the switch.
The solution is to replace the pin switch with a lever switch. The stainless steel lever isolates the pin from the latch: it protects the pin from shear forces from the latch; it is smooth and flat, and it won't dig a hole in the latch plastic cladding. In fact, it is wide enough to ride over the plastic cladding hole in many previously-damaged latches, if any loose plastic is trimmed away and the plastic is smoothed out.
Initial solutions focused on pin switches because it replicated the original design. Also, the first switch proposed (from Radio Shack) was unsealed and prone to failure with exposure to the elements. A pin switch replacement will in fact work OK if the latch plastic cladding is undamaged, but it retains the original design flaw.
Another common failure -- though much less common than the latch switch -- is fatigue failure of the solder joints that hold the main module electrical connector to the circuit board. This is simple to fix by reheating/resoldering each pin solder joint and by finding and fixing the source of the fatigue flexing.
VW apparently has
recognized the issue and redesigned the lock module to use a lever-operated switch. So buying a whole new module from VW is a permanent fix. For my 2003 Jetta wagon (should be the same for all MkIV), these are part numbers:
- 3B1-837-015 AS (left/front)
- 3B1-837-016 CF (right/front)
- 3B4-839-015 AM (left/rear)
- 3B4-839-016 AM {right/rear)
They run about $125-200 each depending on vendor and position; left front is about $20 more than the others. This also includes a redesigned latch piece with a notch instead of a flat spot for switch activation.
Another option is to send your module to
Module Master for rebuild. They charge $75 and include a 5 year warranty, but it appears that they do not use a sealed switch.
You can also roll the dice and try a Chinese replacement module, available from AARodriguez (Andrew) or eBay for $35-50 or so. Who knows whether you'll get a quality module or a
Chinese
Replacement
Auto
Part? Both types come from China, and it's pretty hard to tell the difference. Also, these modules will probably be the old design with the pin-type switch. That said, most people have had good results dealing with Andrew. He says his modules are OEM VW China, so they are probably good quality.
So if you decide that you'd like to repair your original module, here are a couple of good sets of instructions for the general repair process:
Please note that these instructions are old and don't reflect the latest thought about microswitches.
The ideal replacement microswitch would be sealed, lever-operated, and mount in the original mounting holes (non-standard location and spacing). Some have used magnetic proximity switches with great success, but I didn't look into this option enough to document it here.
Whichever kind of switch is used, it needs to be closed (have continuity) when the door is open, and open (no connection) when the door is closed. So microswitches need to be installed using the C (common) and NO (normally open) connections.
Several switches have been proposed. Some that I do NOT recommend:
- The original Radio Shack switch or equivalent, because it isn't sealed.
- Johnson Electric (Burgess, SAIA) V4NSUL, because it is a pin switch, not lever operated.
- Chinese VW OEM switch, an exact replacement of the original switch, because it still a pin switch, retaining the original design flaw.
Here are the switches I DO recommend. Both are sealed, lever-operated, and do not mount on the original holes; so they will require creative mounting (JB Weld). The Johnson switch has wire leads, while the Cherry has solder lug terminals. The Johnson is larger in size and may require some plastic trimming to make it fit. If you don't plan to open the electronics module to resolder your connections, you can clip the wires close to the original switch and solder them on the Cherry switch lugs.
A number of people in this thread used a file or dremel to slot the original mounting holes to accommodate the standard mounting holes on the replacement switch. For example and photo, see page 14 of the
A4 Door Switch Replacement, 1.0 instructions. This barely leaves enough metal so that you can mount a pin-type switch with screws. However, a lever-operated switch requires more clearance; there isn't enough metal on the original bracket to mount them this way. You'll have to use another mounting method, like JB Weld.
turbocharged798 trimmed and bent the lever to make it work.
HERE is his post and photo (look only at the lever; this photo shows wires hooked up wrong). This is very similar to the way VW did it in their redesigned lock module. Did they copy his design?
I did it differently -- see my fix in post #
709.
I hope this helps. None of this is my original thought but rather a summary of contributions from all of you.
