1999 Cadillac Deville Passenger heater vlave

I have a 95 Deville, I believe your 99 is the same, if it is, Caddy doesn't use a heater valve. Just the air duct door. If you pull your glove box out, and look behind it, you'll se a small rod connected to the programer, watch the rod while you press the warmer button to 90 then press to 60, if it isin't moving, then your duct door isn't opening. You can disconnect the rod by grabbing it at the connectiion on the right side (programmer side) and push upward toward the windshield, after disconnecting, push & pull the rod to see if the end that is still connected moves freely. If it does try your heater on hi and move the rod, if you now get heat, then I'd say it's the programmer or the electriclal or vacum connections to it. The programmer cost over $500, if thats your problem, I'd head for the junk yard or ebay. Good luck.