Upon arrival performed a one system maintenance checking heating. Checked all electrical, mechanical and safety components. Checked amp draws, cleaned flame sensor, checked amp draws system is operating properly at this time. Steve mentioned that when a/c would come on it would make a rattle then would go away. Turned a/c on and system came on fine, tested 1st & 2nd stage system is operating properly at this time. I did notice some lose screws causing system to rattle. Tighten up the screws. Homeowner also signed up for maintenance.