why wont my aftermarket stereo stay working after install?

Check for power for the radio memory, usually wired into a cigarette lighter line and change the fuse if needed. If that's good then check the aftermarket wiring harness inline fuse and replace or remove it entirely. Then check the main fuse panel radio fuse and replace if blown. Most aftermarket radios draw more power than a factory, hence they tend to blow the factory installed fuse in the fuse panel. Some radios will not work if there's no power to the radio memory circuit used to hold favorite channels and the time/clock circuitry.

aftermarket worked for one day then wouldnt come on so reinstalled factory which works fine without any fuse changes or anything else. all wires correct cause set time and some stations which held. really got me stumped.

Then the aftermarket radio is defective. Its either a fuse issue, wiring issue with the new radio, or a defective new radio. 98% of world electronics now come from China, and the same radio is made in many differnet plants, but they are not all made to the same standards, and they are not all tested either. That's why a factory stereo costs many times more than an aftermarket model to replace when it goes bad, but the factory deck is designed to last the life of a vehicle, and not just the 1-2 year warranty aftermarket models come with.

I installed a radio and now the lights stay on with no key until the battery is dead, gas gauge drops to "E" and back ?? changed back to stock and still is the same? with no engine codes? any help would greatly be appreciated!! please email me cmay8821@gmail.com

Cliff, the radio isn't installed and wired correctly, the battery drains until the small emergency reserve is activated and then depleted.