My 2004 mountaineer won't start

What do you think might be wrong. Last week a pulley was making a noise but the belt is on. No broken pulley.

Clean and tighten the battery connections if you did not already. Perhaps the alternator is not charging and you can also test the starter.

could very well be the starter sometimes it's that simple

My 2004 Mountaineer exhibits same symptoms: lights come on but no noise comes from starter or solenoid. Headlights are bright. Mechanic has it, says the solenoid is not receiving the code from the ignition key. Battery seems to be OK, has not yet tested the starter. Will advise when he finds the problem.