I pulled the old am/fm unit out of the my kids '84 D50. Every time you hit a bump, you would get a lot of static. Installed a Pioneer unit I had laying around. I soldered all the connections and then used shrink tubing on the joints and every thing powers up normally but I'm getting static over all the local stations and when playing cd's. I'm now thinking my problem is in the wiring harness. Any suggestion on anything I might be overlooking?