I also had an issue with the CPO warranty.... my defroster wasnt working on the passenger side. The dealer said to diagnose they had to take it apart, but if what they found wasnt covered I'd be out at least the $800 labor. I figured what could be bad in there that wouldn't be covered?? Go ahead.
Was one of the blend door actuators was bad. "Sorry that parts not covered, itll be about $1100 total"....
Long story short it turned into an odd ordeal of the CPO customer service saying their hands were tied because the DEALER said it's not covered, and the dealer saying their hands were tied because CPO says it's not covered.
I threatened legal action (and had a good basis for it... ya know, because HVAC/Actuators isnt on the list of wearable items) and finally got my truck back after a few more angry calls.