Mechanics

A/C SHORT CYCLING, HIGH PRESSURE

2010 Ford Fusion

Air Conditioning problem
2010 Ford Fusion 6 cyl Front Wheel Drive Automatic 5430 miles

After driving for 10-15 minutes, highway or city, the compressor begins to cycle on and off; on for 5-15secs, off for 3secs, both while driving or at a stop light, or in park. The computer at the dealer showed that the high press side reached around 250 which is when the compressor shut off, it kicked back on once the hi-press dropped to 200psi. Is there a hi-press switch? The dealer wants to test the evaporater temp sensor. Can this sensor cause these symptoms?

The outside ambient temp was 83 degrees.

Is there a high pressure switch? Should it ever make under normal circumstances? What are some causes for the press to be too high?
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M49195
July 1, 2010.




Hi M49195,

Thank you for the donation.

What is the low pressure?

Excessive freon and inefficient cooling of the condenser are possible causes for high pressure.

KHLow2008
Jul 2, 2010.
Thanks for the reply. I'm waiting for the actual values to both questions from the dealer. They keep teling me the pressures are within specs. It seems like every question I ask they want to run it by Ford.

What should the hi/ low pressures be when running and at rest when they hopefully are equalized?

Is there a high pressure switch? Or do they do fancy magic (math) with the computer & the evaporater temp sensor to calculate the high pressure?

I guess I really want to know how the system works, the window/range for each sensor, and what sensors are really used. The folks at the dealer can't answer any detailed question. For example; what is the range for cycling the compressor if it's the evap. Temp sensor? 33F to 38F to cycle on-off?

Tiny
M49195
Jul 2, 2010.
Without any further data we would have to go be the standards.

The low pressure should be around the range of 30 psi.

When pressure equalised, it should be around 90 psi.

The pressure should take some time to equalise and not quickly after stopping.

There is a high and low pressure switch which would stop the system if either codition is breached.

I will be sending you the description file and hope it can get through correctly.

KHLow2008
Jul 4, 2010.
Hi KHLow2008,

Could you please re-send the description file. My Junk emailbox grabbed it and I accidently deleted it, sorry.

Is this description specific to the 2010 Fusion system?

Thanks in advance for re-sending the file.

Regards,
M49195

Tiny
M49195
Jul 5, 2010.
I have resent the file again. The description of the system was derived from our database for the model.
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KHLow2008
Jul 6, 2010.
Thank you very much. It came through fine and is VERY informative. Is there a schematic of the system available that may also show the locations of the devices?

Also, is there any documentation showing the operating settings/ranges for the temperature sensors and pressure transducers? For example: at what pressure does the high pressure sensor shut off the compressor? At what low temperature does the evaporator temperature sensor turn off the compressor and at what temperature does it allow the compressor to come back on?

Tiny
M49195
Jul 7, 2010.
Data is derived from Mitchell 1 and the iinformation for this model is quite comprehensive but repair manuals do not provide the exact spec as to when the compressor is turned on etc.

Component locations are not grouped into single diagram so it is not possible to post all of them as there are too many.

You may subscribe to Mitchell 1 to gain access to the information. As to the fees, you would have to check with Mitchell 1.

KHLow2008
Jul 7, 2010.

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