I have a 2003 Mercury Gran Marquis and get more help from this forum than any where else. It has EATC. Several months ago I had airflow only through the defrost vent and replaced the small O rings inside the EATC head control unit which fixed that. Now that its warmed up and hot, the AC only works part of the time and seems to be getting worse with the clutch not engaged. At first, I would leave it on Automatic at 60 degrees and after a couple of miles it would start cooling. After it started taking longer and longer to start cooling, I would swith temp up to 65 degrees or back and forth between Max AC and Defrost and it would eventually kick in. Clutch spacing (I tapped it with the system on and it didn't engage) and freon level is OK. I unplugged the wire plug from the low pressure swith on the accumulator and the clucth doesn't kick in with it shorted across. Could the problem be in the EATC controller unit. I am thinking of sending it to the company in TN that rebuilds them. Any suggestions?

 

I had one that the control head would not engage the clutch. Without a proper pinpoint test I couldnt tell you for sure though. Might be time to buy that 700 dollar gorilla.