I see water on the floor of my car which is maxima 96, the rear seat on left side only and it spread out under the driver seat, and the water appear only when it is raining or snow, even if the car is parked

Most likely it's the sunroof...youtube how to fix a leaking sunroof

Leaking trunk seal or rear window sealer also check the tail lights are mounted properly and that the trunk is closed all the way

Check your trunk drainage holes for debris and check your door gaskets. If it is the drains, the water can back up and creep through the back. If it is the gaskets it could be coming right under the door and onto the floor.

its under the radio on the floor. look on the floor right next to the gas pedal. you will see a black side cover. remove the cover and you will see the computer. there is a cover on the passenger side also. right under the glove box next to your left foot if you were sitting in pass. side seat.

This can be from one of couple sources. One would be a broken or missing rubber seal in the firewall. Water can and will enter the passenger compartment if the seal is not good or missing. The firewall is the metal between the engine compartment and passenger compartment. There are many penetrations in the firewall for throttle linkage, steering column, electrical harness, etc. All of these penetrations have seals to prevent water from entering. Check to make sure all penetrations have seals. Inspect from under hood and from under the car, too.

Another source is damage to the floor pan. If you went over a rock or jagged object without having enough clearance, it may have punctured or even sliced through the floor - under the carpeting and sound deadening material under it. If you live in a cold area, and the roads are treated with salt or chemicals to melt ice, it may have caused rusting holes to appear in the floor pan. Water spraying up from tires would enter through the puncture or slice and the carpet would wick the water in. It would take a long time to dry and give a musty smell after just a short time. You should inspect the floor pan from underneath the car. Look for punctures, slices and rust / rot. Clean and seal any openings found in the floor pan and firewall.

Fixed windows and glass in the car body are also sources for leaks. The is especially true if glass has recently been replaced. Many times, the back window leaks into the trunk or metal under the rear seat - and flows to the carpeted floor. Look in the trunk at the bottom of the rear window. Side windows can leak, too - so don't forget to look behind trim interior panels on the sides of the back seat. Your leak could be coming from the windshield, too - this will be harder to locate through the dashboard - but you may find water dripping from wires, etc. Look for evidence of water / rust. Clean and reseal body / glass joints when found.

Good luck!

The drain for the water coming from the ac is clogged. Clean it up. It's easier to do that from underneath the car - the drain is located on the firewall.

Remove the Cowl vent panel under the wipers. Each corner in the basin has a square drainage hole. Make sure they are clear with a blower or long wire. They get clogged with leaves and debris. Test it by pouring water and see if it drains under the fender. Drill additional drain holes if you want, at the bottom of this metal basin. On the back of this basin you will see a large rectangular hole where the air is sucked in for the heater. That is where the water gets into if the drainage is clogged. It then shoots through the vent under the drivers seat, aiming to the rear. that is why you get a wet rear floor.

Two ways...#1, naturally the key. the second way this, the 1991 Maxima has a lever on the left side of the drivers side seat at floor level. Simply pull up on the lever and it should pop your trunk. Goood Luck! I hope you find this very helpful!

The fuel pump IS located in the fuel tank. It is easily accessed in this particuar model, under the rear seat. If you have an arm reat in the middle of the rear seat, you'll need to go in through the trunk. Remove the cover from the the far back, between the back of the rear seat and the trunk space. Remove approximately 4 to 6 screws in the center piece of cardboard that attaches the armrest and rearseat to the cross menber of seperating trunk from seat.
From the back seat, grab the top of the back rest of rear seat, PULL HARD forward on left and right sides . This should disconnect the top. Then, on left + right-sides, toward the lower cushon, there will be a bolt, remove them.
Then pull up the bottom cushion.
In the middle of the floor you have left, where the bottom cushion once was, you will find the top of the fuel pump access. From the top there is a cable that goes toward the driverside, follow it to the connector which should be cover by a small piece of foam. Remember to diconnect the pump before attempting to service or replace it.

There shouls be 2 straps inside the trunk at the top. Both on the driver side but one is for the left side and one for the right side seats. Pulling on the straps releases the 'lock' that should then allow you to pull down the seats from the back seat area.