I don't know if the problem is with radio or amplifier. Antenna, radio lights, station, modes, etc. appear to function. Problem is with sound. When radio turned on, sound comes out for 10-15 seconds then dies out. Audio stores telling me $500.00+ to replace, rewire and new speakers, but I'd rather just get repaired if that's an option. If volume turned up near max, some sound will come through. Also, occasionally if weather very damp, radio may work sporadically. Can anyone offer some guidance? Thank you

The "usual suspect" is the fader control wheel on the center console. If so, many owners whose radios provide four speaker output and fader control, bypass the fader switch by running new speaker wires. Obviously, it could be the radio/amplifier at fault, the speakers or a combination of all of the above. You'll want to make sure which components in the system are working properly before throwing money at it.