2000 mercury grand marquis air conditioner & vent blows hot air

check your flap door in the blower assembly,some cars have a manual and some have electric flap.its not closing and or opening corretly.

Oh boy - big job. The Blend Air Door Actuator is an electric motor on top of the Heater/AC case. All of the service manuals call for 8 hours of labor to pull the entire Dash for access. You can get to it through the Glove Box BUT - If pulling the Air Bag, Glove Box, right side AC register and tubing and cutting the crap out of your arms is ok with you, it can be done in about 3 hours for the beginner. Keep in mind that it isn't the right way and the likelihood of breaking something is very high.

thank you very much, I will give this info to my sons. Mary w

Before you go pulling out the dash or try going through the glove box try this. It worked for me. Disconnect the negative battery cable for about a minute or so and then reconnect it. Crank the car up and see if that works. It resets the computer. So far so good on my end. Hope this cheap and easy fix works for you too.

Tracy is correct it is likely the blend door actuator and it is a big job. If you decide to have it fixed make certain to use a genuine Ford part or you will soon be replacing it again. The blend door actuators made by Dorman are not nearly as good as the Ford part.