2002 Mercury Grand Marquis Q&A
2002 Mercury Grand Marquis Question: No heat or defrost in 2002 grand marquis. Thermostat problem?
Your thermostat is probably not the problem, unless you have an overheating problem as well. You could have a bad heater control valve since your air conditioning is working fine. - Prestige Auto Works
dont have an answer, this wold be my question also 2007 grand marquis - paul catanese