Need Head Unit Install Info

[BRUN]

im having major problems trying to help a friend with his Toyota Avensis

his tape player broke so he got another second hand one, however the loom had been cut so i had to wire onto it an ISO block, which ive done

he also needed a harness adapter lead for his car, Toyota -> ISO

plugged it all in and it comes on, but no sound comes out

ive tried everything and it makes no sense at all, the tape player defo works as ive tried it in the wall of sound rig at work, which made me think it was his car or the adapter harness, its not though as ive tried another stereo on the adapter loom in the car and that works perfectly

someone told me a faulty speaker may shut down the internal amp on the unit, so i disconnected all the speakers on the ISO block and tried them one by one, no sound at all

ive tried adding an extra earth cable to the unit, no difference

voltage is 12.8v, with car running its 14.4v, couldnt ask for it to be any better

tested speakers through loom, 4ohm

i really cant understand what could be wrong, anyone any ideas ????

 

[BrianR]

My bet is you have wired the ISO plug up without observing the speaker polarity.

Toyota use a common earth return on their car speakers, so the other set you tried in the car worked because it was wired correctly.

The Toyota set you wired, worked in the test rig because the rig is wired with separate earth returns, so the speakers would work, they would just be out of phase.

But when you put the set you wired in the car, your shorting the output because its wired wrong, and it will shut down..

 

[BRUN]

so how do i fix it

ive tried every speaker on its own, and in reverse polarity aswell

catch me on MSN mate im really getting annoyed with it lol