Auto Air Conditioning & Heater Repair: AC Repair, irv loev, passenger dash

Question
Dear Mr Hill
I have a 2002 cadillac Deauville. Cool air flows only from
the passenger vents. Warmer air flows out of the main
drivers vent. What should be done?
                      Thank you
                      Irv Loev

Answer
Irv,
The first thing I would check would be your refrigerant charge. If your vehicle's charge is low, it wouldn't be making your evaporator as cool as it should, therefore, there would be a difference in the temperature between your driver's and passenger side vents. With a thermometer, take the temperature of the air coming from the passenger dash vent closest the door and take the temperature of the driver dash vent closest to the door. Your blower on high and the a/c on max. If there is a 9-14 degree difference between the two, then that would tell me that your charge may be low. If it is more than 15 degrees...
If you have the dual-zone a/c, that means that you have two blend doors on your evaporator housing. The blend doors are what mix the cool from your evaporator and your heat from your heater core. (These are mounted in the same housing) It could be that something is preventing your driver blend door from completely closing off your heater core, allowing that heat to mix with the cool air and causing the difference in temperature. There are many things that could cause this. Everything from something as simple as a foreign obstruction blocking the door from completely closing to a weak door actuator/motor, to a pinhole leak in one of the vaccuum lines that control that door actuator (if you have a vaccuum activated system)

So, first, check your refrigerant charge. With the engine on, locate and watch your compressor. Is it cycling on and off? (The front plate of the pulley should be spinning all the time) If it isn't cycling at idle, what about if you rev the engine to approx. 1500 rpms and leave it there for a moment? I believe you will see it engage and disengage now. If so, you need to have a bit of refrigerant added.

If the clutch remains engaged... then I highly recommend you take it to a reputable shop and have them look at your blend door(s). This can turn into a lengthy repair when you are doing it out of your garage, and most shops have the diagnostic equipment to make this task much easier and quicker.

Thank you for your question and I hope that I was of a little assistance. If I can do anything further now or in the future, do not hesitate to ask. Please remember to rate this response and good luck in everything.