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Cadillac Taillight Condensation

By Logan

Problem: GM currently has a service bulletin on Seville lamps - they consider 'condensation' normal in Seville lights- and that they are designed to 'vent out' under way. They do not consider it to be a problem unless the water is leaving 'water strips' on the lens -- Logan

I did see someone posted the cause of the problem. Basically GM has a old bulletin describing what causes the problem. What the bulletin states is the light actually has too many mounting studs. The deck lid itself has flex to it during opening/closing. This is/was causing small stress cracks in the light and hence the moisture. Newer versions/replacements use less mounting studs. -- Logan

Solution 1: Drill holes in the bottom of the lenses I solved my moisture problem by drilling a small hole at opposite ends of the lens on the bottom you have to take the taillight out to do this ...it's been almost a year and it's not had any moisture so far. -- Ron Freeman

This seems to be a chronic problem with Seville's! I put three small (1/8 inch) holes at the bottom of each inboard lens, being careful to drill into the clear outer lens and not the red lens inside. They are not noticeable and fixed the problem, though occasional fogging occurs when I wash the car. Cheap and easy to do! -- CR

When I first noticed it I took apart my tail lights, put a hair dryer to them to get the water vapor out, even put them in the oven, and then put them back on. They looked great, for about a week, then they were fogged up again. I ended up reading a post on this board here that said drill holes in the bottom of the lights between the clear outer layer and the red plastic. So i did that, and since the back lights have looked great. After rain or a car wash the lights fog up, but only for an hour or so. Drilling the holes is a much better deal than buying new expensive tail light fixtures. -- JohnE

There is a fix for the lights fogging up. We have dealt with this on our cars on and off since 1983. Find a spot in the lower part of the light housing, usually on the back of it and drill a small (1/8")hole in the bottom of it. -- Willy

Seems to happen on the 2 center units most-if the problem is with the outer corner lights-they will have to be removed to do this trick- the centers can be done this way- Open the trunk and look at the bottom of the light- in-between the outer clear lens and the inner red lens there is about a 1/8 inch wide black area- you need to drill 1 small hole in this area- start with the smallest drill you have- take just little bites at a time so you can clean the shavings from the bit as you go and not get the shavings into the light- it will take several days for the lights to dry out- they will also fog some when you go thru a car wash but it will be much less of a problem- if the problem persists try drilling a slightly larger hole- the idea here is to promote drainage

Logan www.logandiagnostic.com