96 chevy tahoe, passenger side and rear cargo carpet is wet

This is normally caused by blocked sunroof drains. Do you have one?

https://www.google.com/search?q=2013+nissan+quest+blocked+sunroof+drain

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The divider is generally not sealed at all, just a lump of metal reinforcement, the coolant may have pooled at the rear. The water will evaporate from the coolant mixture but the coolant will stay a long time so it'll have to be vacuumed out, add water and vacuum some more to pull it from the carpet and padding as much as possible. You can verify whether it's coolant or just rainwater by smelling the carpet. You may be nose blind to it by now from driving the car so have someone else sniff the carpet if you don't detect any coolant smell yourself. It'll also feel more slick than straight water if it's coolant so that's another way to ID the liquid. Option three is a cat or dog, they'll likely try to lick it if it's coolant but don't let it clean the carpet for you unless you dislike the animal.

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The two most common causes are rain water leaking in or the ac drain being clogged up. I would vote for rain water if the entire carpet area is wet.
Could be coming in around the windshield, or one of the door gaskets.

DRAIN HOLES IN BOTTOM OF DOORS? UNDER BONNET BELOW WINDSCREEN CAN COLLECT A LOT OF STUFF

sounds like you have a bad heater core

there is either a torn vapor barrier on the passenger door or the sunroof drains are blocked

Check the heater core unit located underneath the dashboard on the passenger side of the vehicle. Even though your car's antifreeze is red, it may appear to be clear when there is only a small amount present. Was the liquid in the vehicle sticky and have any smell to it?

I think that I can help you. It sounds like your drain-tube is plugged up. Get in the passenger side, and pull the carpet back from under the glove box. Look for a black rubber pipe that goes from a black box, and pokes thru the firewall, on the passenger side. Remove the hose from the box, and have a container ready to catch water. If water comes out of the black box, your drain hose is plugged up. Clean out the clog, and you will be golden.

Statistacally--most leaks come from sunroofs and yes they can be one side or the other. Happens from clogged drains. Sunroof drains run across the headliner and down the a-pillar. you can have them cleaned and checked. This is all assuming you have a sunroof. Hope I helped. Thanks.

It sounds like a plugged drain line from the air conditioner. Most cars now run in the a/c mode whenever u turn on the climate control (even when heat is on). The passenger side front is where it would be wet, and the carpet and carpet pad act like a sponge and will soak up the water. Let me know how u make out.