A/C headaches on 2001 Merc Sable

After spending almost $1000 on repairs by three different mechanics, including a dealer, my car A/C still has the same problem: it cools beautifully for 5-15 minutes, then the compressor stops and the system blows warm air. If I shut the whole climate control system off and wait for 15 minutes or so, the cycle repeats. One mechanic checked the refrigerant, vacuum etc. and found it OK. The dealer charged me almost $700 for a diagnostic and replacement of a compressor-to-manifold tube, and when that didn’t fix anything, wanted me to pay $1000 for a new compressor. The 3rd mechanic changed the entire control module - still no success. How do I find out how to get this thing fixed without going broke??

Manual or auto climate control?
How do you know the compressor stops? Do you see the clutch disengaged, or are you just saying that because the cooling stops? (It make a very big difference.)

Auto climate control. I can choose to set any temperature and the system controls the HVAC to achieve that temp.
I meant that I assume the compressor stops because the cooling stops. I don’t know how the clutch operates.

I had a similar problem on a 1990 Ford Aerostar. It turned out that the fan clutch was slipping enough that the volume of air pulled through the condenser was insufficient. However, the fan did move enough air to keep the van from overheating. The technician found the solution by attaching his gauges to the system and then letting the van run until the air conditioning stopped function. At this point, the pressures as indicated on his gauges went way up. He brought his shop van over directed the airstream into the radiator. The air conditioning system started putting out cold air and the pressures went down.

Now, I know your Sable doesn’t have a mechanical fan with a clutch. However, it does have an electric fan to cool the radiator and pull air through the condenser. If the fan is not running, or is turning too slowly to move a sufficient volume of air, this mightbe the problem.

Thanks. The electric fans (there are two) are both running and seem to be OK, but I will have my mechanic check for that when I take it in again tomorrow.

It’s very difficult to analyze A/C problems without vehicle in hand and especially not knowing what the system pressures are, etc.

You might consider having the system run a self-diagnosis and see if anything pops up.
With the engine warmed up, press the FLOOR and OFF buttons at the same time. Very quickly (within 2 seconds) press the AUTO button.
The system will start a self-check and a bunch of gibberish will appear on the display.
This gibberish will go on for 20-30 seconds before displaying any codes.
If it displays 888 things are ok. Any other codes mean a problem, although it is possible for the system to display a “false code” that may have been there since the car was manufactured.

The systems are a bit touchy so it’s possible the problem could be related to a blend door or even a blower motor problem. With the latter, a dragging motor affects airflow and the module that powers the blower.
At 9 years old one could suspect either one of those things. Hope that helps.

I would add that an outlet temperature sensor failure could also cause this problem. The possibility that it really is a bad compressor also exists, but that could be ruled out by doing some pressure/temperature measurements.
You need to go to someone who is good with AC and experienced with Ford climate controls. It sounds like whoever you are using now is just guessing.

Thanks to all - I’m working on solutions based on your comments and will let all know how it turns out.
8/23 UPDATE: I’m now on my third day of consistent cooling despite miserable temperature and humidity in the Boston area. My mechanic dug in after I printed out this string (I had tried the self-diagnosis first, and it came out 888 with no issues). He finally tried adjusting the clutch a bit as he believed it had to be sticking. This appears to have solved the problem and I’ll keep my fingers crossed. THANKS to all who posted responses.
Tom (tombest@rcn.com)