Cadillac Repair: 99 Deville Climate Control, lotsa bucks, floor vents

Question
Problem is passenger side dash & floor vents blow nice cold ac(passenger contol on arm rest)The climate contol on dash seems to be all working , as it auto responds to blow ac when reaches set temps etc BUT all vents on driver side blow warm to slightly hot air. Have to close these presently(manually) and am just using passenger side vents to try and cool car. Anything I can check easily before I have to spend lotsa bucks at dealer? Dad's car, he's 84 and loves his Caddy.
Thanks,
Becky

Answer
Hi Becky, The '99 is a very complicated dual zone system requireing a scan tool to test. About the only thing you can do is operate the system to hot and cold with both controls and see how both sides respond so you can explain to the service writer or tech what is going on and hope it is a simple repair. There might be a bulletin that will help the tech repair this condition if you do take it to the dealer. I wouldn't take your car to a shop that says "we do that". Sorry I can't be more help. Bill