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AC Not Working at Highway Speeds

cmc on Tue May 26, 2009 2:22 AM User is offline

Year: 2001
Make: Ford
Model: Escape
Engine Size: 6 cyl
Refrigerant Type: r134
Ambient Temp: 95
Country of Origin: United States

I had the compressor, drier, and expansion tube replaced because the AC wasn't working at all & one garage told me the compressor was bad (they overfilled it it first, then told me the compressor needed to be replaced). It was so so for the first few days then I drove it on & off the freeway one day & the AC blew warm on the freeway, but was cool at lower speeds & while stopped. I have heard about the fan clutch but that was mentioned for not working at low speeds but working at higher speeds, it's also been suggested that the serpentine belt needs to be replaced. We've already got alot of money into this & can't afford much more, does anyone have any ideas or do either of the ones I mentioned sound right?

Thank you in advance for any suggestions.

mk378 on Tue May 26, 2009 9:49 AM User is offline

Probably the compressor is not engaging when it should under some conditions. This can be for a variety of reasons (that may be hard to find if it only does it while driving), but since it's a new compressor I'd look at the clutch gap first.

Another possibility is it is working too well and the evaporator is freezing up during the highway drive. If that were the case, cooling would not return immediately upon slowing down. If you happen to be stopped and it is not cooling, open the hood and check if the compressor is engaged. This will help in the diagnosis.

The fan is not an issue at highway speed. Also it's not the belt, if it were bad nothing would work.

Edited: Tue May 26, 2009 at 9:52 AM by mk378

cmc on Tue May 26, 2009 8:04 PM User is offline

Thank you for the suggestion. However today when I was driving around it didn't seem to matter about the freeway or city or stoplights. I opened the hood in the driveway & ran the RPM's up & down & it sounded like the compressor was cycling on & off, I put a thermometer in one of the vents & the temp was about 55, by the time I drove the car about 3 miles it was up to 72, then over another few miles would drop down to 60 go back up to 67, then down again & up again; the speeds ranged from stopped to about 50 mph. A friend of my husband said it could be a vacuum switch on the dash or a switch on the compressor that thinks it's low on freon & keeps switching it on & off. Should I have those checked along with the clutch gap or do you have any other ideas?

Thanks again for your help.

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