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John Mc
John Mc, Ford Technician
Category: Ford
Satisfied Customers: 6240
Experience:  19 years Ford Lincoln Mercury experience
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What should the A/C compressor high/low pressure readings be

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What should the A/C compressor high/low pressure readings be for a 2006 Mercury Mariner Hybrid with outside temps at 82 F?

With the climate control set to Max A/C (compressor "should" run all the time) the compressor keeps cycling on and off at about a 10% off duty cycle. I'm showing manifold pressures when compressor is running of 25PSI and 160PSI respectively. When compressor cycles off the low climbs to 35PSI and high drops to 145PSI as the system tries to equalize. If I shut the car off the pressures equalize to 60PSI and 110PSI after about 10 min. My refrigerant pressure charts show I should be reading 35-45PSI and 175-200PSI at 80 F ambient. If I let the vehicle sit idle with Max A/C on, after about 15 min the temps at the inside register slowly gets down to about 45 F.

I just got the vehicle back from having the A/C serviced where they said it was low on refrigerant. They did a leak test which was negative and said they evacuated and recharged the system and charged me $209 :-/. The inside temps never get chilly cold like I get with my other vehicles. With the 100s F days we've had here in DC the past few days the cabin temp never could get below 80F while leaving the controls on Max A/C. If I let the car go into electric mode, kickoff the compressor, then it never could really recover and cool down :-( thus why I took it in to local Ford dealer for service. The service ticket states they add 16 "units" of R134a at $2.09/unit.

HiCustomer I am John Mc, a Ford dealer technician.
I hope I can help solve your problem quickly and accurately.


From your pressure readings your truck is still low on freon. I always fill by pressure and not by wieght. You will need to add freon until the high side is up to 200. Here is an easy rule to remember. Take your ambient temperature and multiply by 2.4 and 2.5. Your high side pressure should be right in that range.


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Thank you,

John Mc

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