You guys are experts,you bailed me out before. Tried to find a mercury website like this one, but to no avail. I have an 89 mercury grand marquis with auto climate control.nice and cold and functions normally 90% of the time. Sometimes the compressor seems to not come on soon enough & real warm air comes out for about 4 minutes & then the comp. Starts & it stays cold. It will do this periodically. There must be a sensor in the car to control this.am i correct & if so where is it & could this be the problem or any other suggestions? Thanks

 

Check your compressor clutch gap first.

 

+1 on ProjectSHO89. Gap should be probably in the 0.014-0.030" range. Not 100% sure on the spec for this old car, but that is a common range for Ford's compressor clutches. I bet you are in the upper range or above. If so, then pull the clutch and remove a shim or 2 to get it back in spec.

 

Thank you guys. This will be my first thing to check

 

There are a few decent Crown Vic sites that will cover your MGM. www.crownvic.net is about the best that I have found -- it doesn't come close to FTE but it can be helpful