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2005 Mustang GT AC cycling on and off every minute

  • Thread starter Thread starter GeorgeSwadling
  • Start date Start date Jul 12, 2025
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    air conditioner air conditioning mustang 2005-2009
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GeorgeSwadling

Member
Jul 12, 2025
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California
Jul 12, 2025
#1
  • Jul 12, 2025
  • #1
Hi All,

First question on the forum, apologies if this isn't the right place!

My AC was not as cold as I remember so borrowed a gauge set from O'Reilly.
I set the AC to full blast and hooked up the low and high pressure hoses.
I observed the AC for about 10 minutes. The system ran on a roughly 1 minute cycle. The compressor turned on and high side pressure rose to ~350PSI while low side pressure dropped modestly from ~55 to ~45 psi. At the 350 psi top pressure the compressor cut out and both side dropped rapidly. The low side then underwent a few oscillations between 25 and 65 psi as the high side continued to fall. The compressor then turned back on to pump back up to 350 psi on the high side. One of these cycles can be seen in the video below.



I had hoped that the system was just a little low on refrigerant but since it wont operate in a steady state I am not sure I can clearly diagnose what is wrong.

The AC air temp appears to fluctuate in temperature from warm to cold. Outside temperature was around 75F for the test.

Any insights would be greatly appreciated!

Thanks,

George
 
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