rear light moisture ingress.....

[britlude]

that age old problem of moisture in the rear lights....

now, i know the usual response is 'get new foam seals' but these are good, recently replaced when i put the new (to me) light units in, and experience tells me that the lights fogging up is usually indicative of dampness in the boot, usually after having to open the boot when its wet and drips rolling off it before you can get it fully open.... and that usually affects both lamps and the centre piece if very unlucky....anyhoo.....

the light now off the car and dried on a radiator for a day (cos no-one here has seen a nsx lamp unit before....)
https://live.staticflickr.com/65535/51708624990_c0b012f9df_c.jpg (https://flic.kr/p/2mMjdH5)Nsx rear light issue... (https://flic.kr/p/2mMjdH5) by NSX Jon (https://www.flickr.com/photos/152809076@N06/), on Flickr

upon cleaning to replace it, i noticed this....
https://live.staticflickr.com/65535/51707750431_0a5f7a7484_c.jpg (https://flic.kr/p/2mMeJJt)2021-11-27_09-59-36 (https://flic.kr/p/2mMeJJt) by jon sutherland (https://www.flickr.com/photos/152809076@N06/), on Flickr

further investigation found this....
https://live.staticflickr.com/65535/51708015298_7781a02cee_c.jpg (https://flic.kr/p/2mMg6t9)Nsx rear light issue... (https://flic.kr/p/2mMg6t9) by jon sutherland (https://www.flickr.com/photos/152809076@N06/), on Flickr


i think this illustrates how the light angle affects the visibility.....

https://youtu.be/6e1ik8RrC3w


close up (making the camera phone really work for it's keep) and in shadow i see....
https://live.staticflickr.com/65535/51707745406_41ca228571_c.jpg (https://flic.kr/p/2mMeHeQ)Nsx rear light issue... (https://flic.kr/p/2mMeHeQ) by NSX Jon (https://www.flickr.com/photos/152809076@N06/), on Flickr

and....
https://live.staticflickr.com/65535/51708015218_9e77781cb4_c.jpg (https://flic.kr/p/2mMg6rL)Nsx rear light issue... (https://flic.kr/p/2mMg6rL) by NSX Jon (https://www.flickr.com/photos/152809076@N06/), on Flickr

i can feel then with my nail, so very small isolated areas of fine cracking of the plastic.... annoying as i changed out the old light units because of the crazing on the top edge at certain light angles

so is this where the moisture is getting in?? maybe as this side was very wet, the other side bone dry

someone has suggested UV has caused this... i do have some screen repair fluid en-route to hopefully seal the cracks... i do have some Capt. Tolley's creeping crack cure,

https://apollomarine.co.uk/wp-content/uploads/2016/08/49200.jpg

but as that is white drying clear, i'm a little concerned it might not dry out deep in the cracks and leave white artefacts, at least the screen stuff is clear at all times... i shall experiment!

[Heineken]

These do look like micro-cracks. They are typically induced by mechanical stress or UV light and can be seen on many old camper windows and similar.
Since these usually stay tight, I'm not sure if that's the reason for the water ingress.

My old BA4 Prelude had water issues at the rear light, too and the seals where actually part of the problem. Water entered the light at plastic seams and couldn't escape since it was sealed in. After cutting the seal at the bottom it was able to escape and my trunk wasn't subject to becoming a swimming pool for the emergency wheel any more ..

[Old guy]

The only thing that could have been better is if it had been Captain Colley's Creeping Crack Cure. I love a good bout of alliteration.

I can't confirm the nature of your crazing; but, it definitely looks like the crazing on the plastic headlights on my son's 2005 Acura RSX which is parked outside all the time so gets plenty of sun exposure. My NSX had scratching along the top side of the taillight; but, I expect that came from a previous owner with long fingernails opening the trunk. In the case of both my tail lights and my son's headlights, some time spent with a DA buffer and some Meguiars 105 and 205 compound eliminated (my tail lights) or greatly reduced (the RSX headlights) the defects in the plastic. In my case, I had some left over pieces of 3M PPF which I used to wrap the top portion of the light to prevent future scuffing. With just a little more work you could wrap the complete lens surface which would definitely seal the surface for you. You can purchase small quantities of PPF on Amazon and EBay for a reasonable price. 3M and others make a sealant for restoring plastic headlights and providing UV protection after the lenses have been polished which was what my son was going to do. However, he was the victim of a red light runner who clipped the front of his car destroying the bumper cover. The headlight lenses were not damaged; but, the impact broke the headlight assembly mounting tabs so he is getting new lights (and bumper cover) courtesy of the insurance company. Not a recommended way to fix the problem!

As a final note, I recall that the tail light assemblies are not sealed. There are vent holes and if you have trunk water ingress issues this is probably contributing to water ingress through the vent holes. This is assuming that you don't have splits in the seam between the front and back section of the lights where the water is entering. If you are still using conventional incandescent light bulbs, driving around with the lights on will probably generate enough heat to eventually dry the interior - that is why the light housings have the vents to stop them from bulging as they heat up. This definitely will not work if you are running LED tail lights.