Will not loud disc - Car Audio & Video

This is assuming this isn't a power supply problem ie wiring or car power level too low.

With car players they tend to have problems with the gears inside the player. They also can get jammed up by dust. Unfortunately you only have a few options here. You can clean the tray and gears using compressed air (not too aggressively as you don't want to blow the dirt or gunk into the gears)
What happens is the gears will get a build up of dust and the gears will take more power to and the controller sees this as a jam and stops the load. The gears can also break or chip from UV or heat or just too much force being used to close the tray.

Unfortunately if the cleaning doesn't work then your only real option is to replace the unit. If you could take the unit apart you might be able to clean and re lubricate the gears etc but then that doesn't always work.