1989 volvo 760-gle stereo

I am working on a 1989 volvo 760-gle.My problem is the customer bought a radio of this guy and installed it.now he claims all the speakers all worked at one point and after the guy installed the radio he said the two front speakers was the only working speakers.Now he came to me and asked me if I can help him I said I will take a look at it I pulled out the scemetics from it and hooked evrything up and all I got was a humming noise but the radio turned on and when I disconneceted the radio the humming noise continued.He says there is a factory amp. I run the wires and ran into a box saying boosh I think that is the amp causing the problems.please help.thanx  dave25456

I really need help .What should I do? run everthing direct or is there a way to bypass the speakers to the radio?dave25456

dave25456 wrote: I really need help .What should I do? run everthing direct or is there a way to bypass the speakers to the radio?

also how do dissconnect the factory built in ampdave25456

you're putting an aftermarket h/u into this volvo, correct? there should be a factory amplifier to the left of the steering column under the dash. just unplug it and find all the speaker wires there....lead your h/u's speaker outputs to these speaker wires and it should be all good. good luck!

thanxs for the info guys really appreciateddave25456