Water pouring out of mirror?

Strong thunderstorms this morning. On trhe way to work after the rain had stopped, water starts pouring out of the bottom of the rear view mirror and falling on the dash! Luckily we had a bath towel in the truck. Where can this be coming from? The windshield seal? The Onstar antenna? anyone heard of this?
Thanks,
Robert

Do you have a sunroof or the marker lights up there?
 
It's gotta be a glitch of some sort.  I have had strong rains and no leaks.  I have a sunroof and the GPS antenna but no marker lights or other potential leak spots.  I guess it could be the windshield seal, especially if the windshield has been replaced without proper care.
 
I' m sure you'll get more comments from others, but keep us posted.

Never heard of this, I have had a leak but it was always by the rear doors.  Do you have roof marker lights like TexH3 asked?

Just currious, did ya get a message on the mirror that said wet????

Sure it wasn't the 'Rain Gauge' feature??
 
Cliff

Most likely culprits are the sunroof, marker or off-road lights.

After the rain, I got up there and looked really good. Cannot believe it is the windshield. No roof marker lights. The OnStar antenna is off to the RH side and the leak was dead center of the windshield. For the life of me I cannot figure out how it got inside of the mirror. The water was actually coming out of the bottom of the mirror. Do have a sunroof but it is really too far back, and it looks really tightly sealed. But there are plastic trim pieces that come up at both sides of the windshield and join the horizontal trim plastic that runs along the top of the windshield. There are definitely gaps and holes where these pieces join. Just wondering if this is normal. Guess we will have to run this in to the Stealership to get it checked out.

quote:

ORIGINAL: RMD
 water starts pouring out of the bottom of the rear view mirror Where can this be coming from?

 
If the water is coming out of the mirror I can think of only one place it can be coming from. I'll bet the OnStar antenna is leaking and somehow the water is getting inside the antenna wire that goes to directly to the bottom of the mirror. There is no other way for water to get inside the mirror. My money says it's the antenna wire that goes into the bottem of the mirror which is filling up with water from the leaking OnStar antenna on the roof and in turn leaking out of the mirror.
When you get it fixed let us know exactly what it was and where I can collect my prize. lol
 
Be sure to tell them how the water damaged the dashboard, stereo, carpets, and everything else you had piled on the dashboard including you laptop computer and that everything needs to be replaced on their dime.
 
Gar

Consider this,  The water could be coming through a small hole above the mirror, running down the windshield in a very thin stream and collecting on the mirror after running down the connecting stem to the glass. 
 
It's a guess

The GPS antenna has a triple seal (2 rubber seals and an o ring) on the bottom and I would rule it out immediately.  If the windshield was leaking, I believe it would run down the window, and not up into the headliner. 
 
The upper roof support (above the mirror, inside the headliner) is an empty cavity that runs the length of the windshield.  If there is a leak anywhere on the roof, with the front end being slightly lower ther the rear, the water would naturaly gravitate to this area, and since the mirror wire passes through the headliner to the mirror, water will collect at the lowest possible spot. 
 
Have the dealer pull the headliner and the outside plastic on the roof, roof marker lights and windshiels trim, and start looking for trace signs of water. 
 
Had a friend that his Z71 Tahoe devoloped the same problem, and they finally found a screw on the roof rack hardware that had backed out enough to let water in. 
 
Good luck 

Check the sunroof drains. If they're clogged or have an obstruction of any kind it could cause a water leak into the vehicle. typically not by the rearview mirror but anything is possible.