I had the same thing in my 2000 Chevy Silverado with the factory HU. You could turn the volume knob either direction as much as you wanted. If you kept turning it lower, the volume would completely silent, but you could keep turning it. Then, if you turn it back up, even a little, the sound comes back in. When you turn it up, the output will reach a certain level and then stay there even if you continue to turn the knob. I actually found that if you turned it as far as the sound would go, and then backed off a few clicks, it would actually be a little louder than at the 'full' level. Dont have to worry about any of that anymore though Just miss the speed compensated volume.