This is why your Hummer Leaks In the Rain
 

The roof rail channel drains over your side roof light connection this rag shows where it goes

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Water escapes here to run down the inside of your door rubber or to be more accurate its just left to go wherever it chooses .

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Door rubbers are stuck on with ..... MUD !

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While your up there tear the gasket off the bottom of your roof light its a bloody sponge

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A bead of silicone means water will never get under your marker light though it doesn't really matter as the roof rails are designed to drain under the light any way .

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The one pic i forgot to take is of the big blob of gutter sealant i put on top of the the rubber grommet to ensure water bypasses it . Now i need to remove the rubber door seal and the one on the plastic roof trim , clean all the crap out and glue them tight into place so mud or water cannot get behind them .

If your leak has just started pull the windscreen column trip and clean out the accumulated leaves and mud and whatnot from the gap at the top . This slows the drainage of the rail channels allowing them to fill up with water to a level higher than the grommet letting water in .

I have a thread about sealing the a/c intake somewhere, sorry can't figure out how to paste the link. It's called new culprit for soaked passenger floor. Check that out while your at it....

Shayne thanks for the right-up. I will pull my lights up and silicon under them. I pulled my weather strip off back in summer and cleaned mine all up in the laundry sink with cleaner. They also were packed with crud like yours, my leaking or little water drops on my inside pillars seems to have stopped..for now.

I can't be 100% sure but i think the a/c is an entirely closed system it takes air from within the cab cools it and blows it back . If you have water coming out of it i would guess it just happens to be the route water takes from your leaking roof , or possibly a condensation build up within the a/c itself . Either way i would not choose to block it up as it only means water will be forced to find another route possibly over far more important electrics .

The water actually comes in from around the intake located on the outside passenger side under the windshield wiper cowl, not from the a/c itself. The drain exit out of the firewall for the sunroof drain is actually right above it...
It comes in down the firewall and pools up on the passenger floor. You're just sealing the outer edge of the intake hole -not actually blocking anything up.

https://www.hummerforums.com/forum/h...culprit+soaked

Ah i missed that thanks dieseldrums i guess thats another design error i will have to investigate and remedy . If i didn't know better i'd swear i was driving an untested prototype seems the basic vehicle was built to be bullet proof and they then contracted a third world toy factory to to fit the the interior and trim :(

Under that light has been the biggest pain of my life with the H2. After a snow when the truck would sit in the sun the snow would melt, follow that path, and refreeze in the door jam. I would come back to a frozen door almost every day. I even have water leaking through the grab handle bolts, by the looks of it it's all the same leak.

Yeah, well what do you expect for a $60,000 vehicle (priced in 2003)...

That leak took me a while to track down! I had to also change out my a/c fan that was full of water.

Don't forget to seal the molding under the side pillars if you haven't already. I'm sure you have had the "rattle" driving down the road.

Actually they started at 48k per my window sticker, fully loaded mine was about 53k total.

The last i remember 54k ish was the base model .