Tail light lens seal, where does it go? Options

[vitamin914]

I need some guidance with installing the rubber cord seal from 914Rubber on the tail lights.

The lenses and reflector housings are replacements from AA. The OEMs are too far gone with no reflector chrome and corrosion in the sockets.

It seems the contour of the lens isn't a perfect match to reflector housing (even on the old OEM housing). There is a gap mid way at the top (see first photo). The gap sort of disappears if there is no rubber cord when the lens and housing nest together. Adding the rubber cord makes it worse as the lens does not seat as deeply. This also raises the question... Where does the rubber cord go? Does it go in the housing or does it go in the lens? (last two photos)

I really want to stay away from using RTV silicone if I ever need to change a bulb.

[914sgofast2]

After reading this thread, I decided to have another go at making my taillight lenses seal without a gap. I tried gently stretching the new seals from 914Rubber. That made the rubber cord seal smaller in diameter and it fit better into the slot in the lens.

The lenses I have are the Hella 3-color style (amber, red & clear). Stretching the rubber cord seal did the trick and the lenses now fit without the pronounced gap between the lens and taillight housing. No more need to cover the gap with a small piece of black electrical tape, as I had done before. Before the idea dawned on me to stretch the rubber cord seal, I looked online at Grainger Supply and ordered some soft silicon cord, but that won’t arrive for a month. The soft silicon cord has a durometer measure of 40, while the rubber cord and regular silicon cord has a durometer measure of 70. When I receive the soft silicon cord, I will report back on how it works.

By the way, my Hella lenses have both been broken at the seams where the different colors of plastic meet and been repaired with gap filling crazy glue in the past, so they are not exactly factory “straight.”

[vitamin914]

After reading this thread, I decided to have another go at making my taillight lenses seal without a gap. I tried gently stretching the new seals from 914Rubber. That made the rubber cord seal smaller in diameter and it fit better into the slot in the lens.

The lenses I have are the Hella 3-color style (amber, red & clear). Stretching the rubber cord seal did the trick and the lenses now fit without the pronounced gap between the lens and taillight housing. No more need to cover the gap with a small piece of black electrical tape, as I had done before. Before the idea dawned on me to stretch the rubber cord seal, I looked online at Grainger Supply and ordered some soft silicon cord, but that won’t arrive for a month. The soft silicon cord has a durometer measure of 40, while the rubber cord and regular silicon cord has a durometer measure of 70. When I receive the soft silicon cord, I will report back on how it works.

By the way, my Hella lenses have both been broken at the seams where the different colors of plastic meet and been repaired with gap filling crazy glue in the past, so they are not exactly factory “straight.”

(IMG:style_emoticons/default/agree.gif)
I did much the same thing - I stretched the cord so that it would seat deeper in the groove, then pushed it in so that it bottomed out with a popsicle stick. That let the lens seat deeper into the housing allowing that wow in the lens to "disappear". I also put the ends of the cord (where they meet together) at the bottom of the lens. If for some reason the cord decides to shrink back and creates a gap, being at the bottom it will just act as a drain hole rather than let water in if it was at the top.

Here is my concern. The purpose of the cord is to seal against the housing to keep water out. For it to seal, the cord has to conform and touch the housing. With the way I did this I think, where I have the wow in my lens, there is no seal against the housing so water will still get in through that spot. I did get rid of the gap...

To seal properly, the cord has to move in the groove and compress to allow matching to the housing. This won't happen if the cord is too stiff, or too tight in the groove. I even thought about dusting the cord with talc or using glycerin to allow it to move easier in the groove. The way it is now, the plastic lens and 3 screws are not strong enough to give uniform pressure on the cord all the way around.

Mark @mikey914 (914Rubber) has a really good idea about making the cord from an even softer than 40 durometer rubber. I hope he can find the time to try it.

[Mikey914]

After reading this thread, I decided to have another go at making my taillight lenses seal without a gap. I tried gently stretching the new seals from 914Rubber. That made the rubber cord seal smaller in diameter and it fit better into the slot in the lens.

The lenses I have are the Hella 3-color style (amber, red & clear). Stretching the rubber cord seal did the trick and the lenses now fit without the pronounced gap between the lens and taillight housing. No more need to cover the gap with a small piece of black electrical tape, as I had done before. Before the idea dawned on me to stretch the rubber cord seal, I looked online at Grainger Supply and ordered some soft silicon cord, but that won’t arrive for a month. The soft silicon cord has a durometer measure of 40, while the rubber cord and regular silicon cord has a durometer measure of 70. When I receive the soft silicon cord, I will report back on how it works.

By the way, my Hella lenses have both been broken at the seams where the different colors of plastic meet and been repaired with gap filling crazy glue in the past, so they are not exactly factory “straight.”

(IMG:style_emoticons/default/agree.gif)
I did much the same thing - I stretched the cord so that it would seat deeper in the groove, then pushed it in so that it bottomed out with a popsicle stick. That let the lens seat deeper into the housing allowing that wow in the lens to "disappear". I also put the ends of the cord (where they meet together) at the bottom of the lens. If for some reason the cord decides to shrink back and creates a gap, being at the bottom it will just act as a drain hole rather than let water in if it was at the top.

Here is my concern. The purpose of the cord is to seal against the housing to keep water out. For it to seal, the cord has to conform and touch the housing. With the way I did this I think, where I have the wow in my lens, there is no seal against the housing so water will still get in through that spot. I did get rid of the gap...

To seal properly, the cord has to move in the groove and compress to allow matching to the housing. This won't happen if the cord is too stiff, or too tight in the groove. I even thought about dusting the cord with talc or using glycerin to allow it to move easier in the groove. The way it is now, the plastic lens and 3 screws are not strong enough to give uniform pressure on the cord all the way around.

Mark @mikey914 (914Rubber) has a really good idea about making the cord from an even softer than 40 durometer rubber. I hope he can find the time to try it.

Problem is that the softer material expands significantly when extruded under pressure. I need to calculate where it should be to get the dimension correct, then go smaller and work out temp variables to try to nail it by making small modifications. This material has more variables and I’ve got material inbound to start the process. Tool steel is getting expensive.