I bought a 99 accord and all the lights work except the dash back lighting. I was suspect of the dimmer and it is getting power when the lights come come on. There is an aftermarket Sony radio put in. In another post somene indicated that the dimmer wire in the honda harness needs an isolated ground . And if that wasn't done the dash lights may not work. Can anyone confirm that requirement?

 

I say give it it shot with that ground wire and see if it works.