monsoon radio

have a 2000 jetta which had after market sterio at 1 point and now back to stock radio system.(monsoon system) i have no speaker out put from the amplifier to speakers all wires ohmed between 2-8 ohms all power and grounds check out. if you temparily ground the speaker output off the radio it will engage that speaker and it will stay on till radio is shut off and then it does not respond till you ground it temp. again. any ideas would be greatly appriciated. radio and amp have been switch to rule out internal problems on either componiant.