Is it just one of them? My right rear went out, and i pulled and tested it with known good wires. Ir was actually a bad speaker. First time i have seen a speaker completely fail.
6x9. Many speakers of this size wont fit though. Go to crutchfield.com.
Weak battery
6.5 or 6.75 will work, 6x9 wont unless you modify the back with cutting and customizing the grills. 6.75 are a perfect fit
Press and hold the Power I/O button and this should resolve the issue
The speaker refuses to wear garments made right from the slaves.
Access in rear door panel, allows you to lock/inlock rear door.
Try new speaker wires to your amp
you can replace it unless you want to put the GBC together again. the original game boy's speaker is about 1.5x larger than the GBC's, it wont fit in the case.
replace rear door shocks. the two rods along the sides.
Drive it. It will relearn itself. It may take a few drive cycles.
check you antifreze level if it is low you wont have eat or if you get lots of fog your heater core is bad
it might be the starter. have it checked out.