How to fix heat in a grand marquis follow me on twitter headsavage1. While there are a variety of reasons your mercury grand marquis air conditioning wont work the most common 3 are a refrigerant leak an electrical climate control issue or a problem with the air conditioning compressor 37 how do i repair the air conditioner control 20. A mercury grand marquis ac diagnosis costs between 53 and 67 on average get a free detailed estimate for a repair in your area. Mercury grand marquis car ac repair orlando florida thank you for sending a competent respectful helpful mechanic i dont know how you find these individuals but there certainly is a shortage of them in the shops. Open the hood of the car locate the air conditioner service fittings the low side fitting is used to charge the unit it is found on the black hose that goes from the compressor to the accumulator the fitting looks like a little valve refer to the 1996 grand marquis repair manual for an exact diagram if needed