Why is my Nikon D3300 producing all black photos when my flash is off?

My pictures come out fine when I have the flash open and on but when it's closed my pictures come out pitch black even when it's sunny outside with great lighting. I just purchased this camera brand new from best buy a month ago. But the return policy is 15 days. I'm just worried I wasted 400$.

You need to check your settings- try taking some pictures in "Auto" mode and see if those come out. If they do, then it indicates you need to start checking your settings. You may need to go on a short course to learn how to use a DSLR properly. A DSLR is not a point and shoot and requires you to learn a bit and understand how the different elements work together.

It seems that you are not using the cameras lightmeter to adjust the shutter speed and lens aperture.

There's NOTHING wrong with the camera. You just need to spend more time learning how to use it properly.

Here is a link that should help you learn how to balance ISO, shutter speed and lens aperture

Return policy is 15 days. Warranty is for a year. You are still entitled to free repair and most probably free replacement parts for up to 3 months.

Are you sure you're setting the camera correctly? Set to Auto mode, Auto ISO, Auto White Balance, make sure exposure compensation is at zero then bring the camera outside under the sun and take a picture of a brightly colored car from about 10 feet. If that does not come out right without flash, then hurry back to the store where you bought the camera from. Don't forget the sales receipt.

A number of factors you have not provided make it impossible to give an answer. What settings are you using, exposure mode, iso, etc… Assuming you are using the kit lens, have you attached it properly, is the lens cap on? Try putting everything in Auto mode and see if you get results, sometimes it's easy to accidentally knock one of the buttons or settings out of place so I would start with that.

Your shutter speed or aperture is probably way to small and not allowing enough light in. If you are in Auto Mode and this is happening then i do not know what is wrong at all! I bought a D3300 a couple of weeks ago as my first SLR and it works fine

If you will read the Getting Started section of your camera's manual, you should be fine. If you don't read the manual and learn how to use your camera you will forever be having frustrating problems like this.

Sounds like lack of understanding about how to work the camera. Just set it to "Auto everything", especially Auto Exposure (probably called Program" and shown as "P" on the dial and Auto ISO, and make sure the Exposure Compensation is set to Zero (not + or -).

Then try photos in sunny daylight, dark shade, indoors without flash, etc. You should get well exposed photos in all cases, though those taken indoors might be blurred by camera movement.

If you do not get well exposed daylight and low light photos, then go to someone who knows about cameras, maybe a local photo retailer, and ask advice, before you think of returning the camera. The perfect flash photos indicate that the camera is generally working, so I suspect "operator error" of some sort.

May be you not using lightmeter or may be electrical fault so go and check with service center