Wiring is almost always most frustrating thing to work on. Continuity tester and few other basic tools can help in troubleshooting. Also having bad ground can cause problems
EDIT: after reading your post again i'm thinking that one way or another it's actually not getting the right signal. Something in the wiring is wrong. It's like it's hooked up to the wrong source like a battery and it reads constant value.
Last edited by yevgenievich; 09-18-2008 at 01:49 AM.