I had a similar problem with my '94 original stereo. It turned out to be a poor connection between the two circuit boards which are at right angles. After resoldering the connection it worked but still erratically. I finally gave up and sent it to Clarion Corporation which repaired it for a flat $80 fee and this after I had blown out half a dozen transistors due to a short I made in the tight space of the chassis. That was eleven years ago and it has worked perfectly ever since. You can find them by Googling "Clarion". If they still do repairs I'm sure it will be considerably more than $80 but it still beats buying a new system.