only left side working

[madalpinestar]

hey, i hope this hasn't been asked already iv tried to find it.

I have a vt commodore that I had a pioneer head unit but only one side worked but before I put it in I had the original which worked fine.. I was told it was the head unit so I bought an alpine which did the same thing. Another strange thing is that when I use the aux on the original head unit it goes back to only using the left side

any help would be appreciated

[KAL SPL]

Does it do it on radio , cd and aux ?
Did you buy an adapter harness or wire it in yourself ?