If I turn on my radio with key on and engine off, radio works fine. But, if I then turn my engine on, radio goes off and then on and off repeatedly until I can turn off manually. Same if I turn engine on and then the radio on---it goes off and on until I can manually turn it off. If I travel for about 15 minutes and turn the radio on-no problem. I had relay replaced just in case but no help. Something is obviously shorting out but why does the radio work perfectly with the engine off and also after about 15 minutes of run time?

Help!

 

One thing you can test is how much voltage is showing at your battery posts, or right behind the radio at its harness if you have the appropriate keys to remove it. Test it while the ignition is on and engine off and then with the engine is off, if your getting a reading of over 14.4v with the engine running then you should have your alternator checked. Also look at your battery for swelling (as if it where bulging on the sides). If everything checks out however you might look into replacing the radio, it isnt very hard to do in that car and the parts are minimal.