Sliding Door Latch

[hkpierce]

The sliding door latches are driving me nuts. I am on my fifth one – over $250 worth for the same part. So I apologize for this rant of a post.

How do the latches break? Most instances I attribute the breakage to the door being pounded shut too hard. But review of the damage implies other factors could be involved.

1) Rear Nylon Pocket Break. If the nylon pocket breaks near the rear mounting post, it is as good a dead. The nylon pocket will move such that various springs will no longer remain set, and the metal mechanical pieces of the latch will not operate properly. I think this breakage is attributable to door closing with irresponsibly extreme force. Throw away and be glad there if there is no other damage to the door.


Latch Fatal break.JPG

[hkpierce]

2) Pocket split. This seems to the most common serious damage. The latch basically continues to operate. But the dogs can hang-up, the rebound rate increases and it is often nosier than new latch.
Latch Pocket split.JPG


So, how does this split happen? I see three possibilities:
a. Playing with a new latch, I found that that the pocket contains a rubber bumper at the extreme limit of the bar inside the latch. The rubber is apparently there to reduce noise. However, the metal dogs that clamp the bar have tight tolerance. The rubber bumper can be so far forward as to impede the movement of the bar into position that the dogs can lock – the dreaded rebound then occurs.

Latch rubber bumper.JPG
Latch Rubber b side.JPG


The bar’s progression into the proper position also can be impeded by the 1/8-inch extension side support of the bar, which hits the rubber bumper before the bar gets there. Below is a picture of the bar to illustrate:

Latch bar.JPG


My old latch’s rubber had marks indicting the later event was happening regularly. Stopping the rebound by hand and by forcing the door shut, I speculate, distorts the nylon pocket and may eventually rupture it.

b. Some of my nylon pockets showed wear on the far vertical wall, implying that the bar’s side support was rubbing up against the wall. Note that the sliding door closing action upon hitting the bar is movement forward and then a rotation into the van as the hanger swings the door in. Note that the bar has a wedge spacer to use in combination with positioning the bar vertically and horizontally. I suspect that if the wedge is placed too far under the bar it pushes the side support too far out. But I also have found putting the wedge spacer too thin can result in the dogs hitting the support bar before the rotation occurs.

c. The roof of the pocket also was marked. This meant the bar’s side support (which extends about 1/8 inch higher than the bar) must have been hitting the roof. There are two ways this can happen. First, if the nylon pocket is pushed back too far, the pocket distorts (to the point of the pocket sidewall’s lip moving inside the metal casing of the latch)) bringing the roof down. Second, if the bar is rotated so the top of the supporting bar is not horizontal [the rear of the bar’s base is high relative to the bar’s location], the 1/8-inch material will jam into the roof.

[hkpierce]

3) Nylon Back up lock mechanism. There is a nylon back-up locking mechanism for the dogs when they are engaged around the bar. This mechanism is mounted on two points – a wire and a small nylon post directly under the banging dog. Well, guess what happens? That poor post does not stand a chance and breaks.
Latch bottom break.JPG


When the latch is opened, the dogs are spring-powered open. But the lower dog does not bang into metal. Rather, it bangs into the nylon back-up lock mechanism.


Latch nylon bumper.JPG




So the first of the 2 dogs rotates too far down upon opening. When ready to close the door, that dog hits the bar with either a resulting rebound or grinding noise. As can be seen on one of my broken latches, the bottom dog has hit metal-to-metal so often it has left a visible mark.


Latch broken bumper.JPG

[hkpierce]

Preventive actions and Repair

I now have a couple of spares, so I decided to try some preventive actions on the nylon pocket.

To strengthen the nylon pocket for both rear and side breaks, I used hot glue to add material (and hopefully strength) to the rear mount, side-walls’ vertices, and two cavities fore and aft of the pocket.

Latch glue.JPG

Then I used a Dremel to remove material from the rubber bumper to make room for the bar’s side support.

Latch dremal.JPG

Now what about the wounded latch with the split side? It still works after a fashion. I again used hot glue on the same spots as with the new latch.

In addition, I used a 1/16th drill to pilot-hole into the nylon back-up locking mechanism, inserted a eschion pin, then hot-glued the pin in. I don’t think the later repair will work, as I suspect the forces of the opening dog are too great.

Latch Pin.JPG

Latch Pin 2.JPG

[hkpierce]

When reinstalling the latch, pay attention to the cable and the handle's mechanisms. If the cable or the handle mechanism do not properly and easily return to the neutral position, it will cause the dogs on the latch to not lock in either their first (safety) and closed positions. This is especially true in cold weather when the grease on all the mechanisms can get stiff. When the cable is slow to return to neutral, when you try to close the door, the door will rebound - neither the dog's safety nor final positions will engage as they are hung up by the still engaged cable.

[hkpierce]

When removing/replacing the latch, I find it easier to simply remove the door: http://www.sprinter-source.com/forum...t=sliding+door

However, if you do not have an extra pair of hands to help: If the van is a passenger van, move the first row of 3 out of the way (two rows if the second row is a set of 3) to access the latch from the inside. When remounting the latch, use this technique:
PC181735.JPG

Also, when removing the latch, it slides out much easier if the dogs are in their closed position.

[video24]

For the past 2 years I could not use the door under 40 degrees F......Thanks for the fix.

[glasseye]

hkpierce, you are hereby dubbed "The Slider Doktor". Thanks for the excellent diagnostics and supporting documentation.