I was able to get my Fiero subwoofer all set up today and I think I did a heck of a good job with the wiring and installation.
I have it all hooked up then notice the adapter from the new wiring setup to the radio is the original setup. I had upgraded
my original Delco tape radio system to the newer Delco cd radio system and the connections are totally different. I have
the proper adapter and it worked fine before I changed to the subwoofer wiring so I figured I could still use the adapter.
All I get is a loud quick repeating thumping sound from the sub...can I use this adapter and are they compatible?
Any help is appreciated...

Are you using the factory Fiero amp? It has odd wiring, multiple power inputs.

[This message has been edited by Mike Gonzalez (edited 03-31-2015).]

Yes everything I am using is original except for the sub speaker, I put in a new one from Rodney Dickman.
I have it all hooked up with performance sound slider too and I tried to see if the sound would go down and
no luck , just loud thumping irregardless of the level on the slider...

I think that with the later factory decks you need to add a relay as the radio doesn't supply enough power for the sub amp

I think the wiring harness /adapter I have may be wrong. After connecting the main or big black connecter end, the
other end or the one to the radio mine has 5 different connectors and only 2 go to the radio: The longer black and small blue
fit to the radio and the white which on my adapter is joined with another black connector goes back to the car believe it's
the Power one. That leaves 2 connectors both black to radio not used at all but are wired in the harness..any help?

I found the link http://fieros.de/en/articles/sub.html