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I was helping a friend yesterday with their E53 X5's AC system when I noticed this strange behavior:

  • Before turning the AC on for the first time both high-side and low-side pressures read the same
  • After turning the AC on the high-side pressure reading went higher and low-side went lower (as expected)
  • After adding some refrigerant via the low-side charging port and turning the AC off the high-side and low-side pressures did not equalize immediately as I have seen it do on other vehicles. After 2-3 minutes there was still a healthy 60 psi difference in the two readings

Is this behavior indicative of something? A clogged expansion valve, perhaps?

  • Check expansion valve – Solar Mike Jun 5 '18 at 7:08
  • If the system was cooling then expansion valve can’t be clogged ... – Solar Mike Jun 5 '18 at 7:15
  • Has it got rear AC? – Al_ Jun 5 '18 at 7:50
  • I have to confirm, but I believe it does – Zaid Jun 5 '18 at 8:03
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    Cars that recent, with such big AC systems, usually feature solenoid valves to shut the flow to both front and rear. Especially with the newest electronically controlled variable displacement compressors (with buses, usually featuring a very large fixed displacement compressor for the entire bus and no separate compressor for the driver, passenger AC has to be turned on before driver AC can, instead). That way, equalization won't happen. Equalization may make liquid from the condenser travel into the compressor and immediately slug it at startup. – Al_ Jun 5 '18 at 8:37

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