I have a 2005 Subaru Legacy GT. The AC pumps a little cold air and then blows only at room temperature. I understand there are two sides to an AC system (high and low) and that the exchange valve and the compressor are the two points where those two side connect to each other. I just replaced the evaporator valve ($30 part and a little bit of labor, but relatively easy to access on the fire wall in the engine bay). I am wondering how I test if the compressor is working...it is not making any strange noises and the clutch appears to engage/disengage the pulley on command. I'd rather not have to replace it if is functioning properly, but don't know how to tell. Any thoughts?


1 Answer 1


You can confirm that the air-conditioning system is working by using a pressure gauge to verify that both low-side and high-side pressures are in the expected range of operation (while the A/C is running and compressor clutch is engaged).

The 2005 Legacy service manual says that a fully charged system should be 400 ± 30 g (0.88 ± 0.07 lb).

The manual also says that under the following conditions, the low-side pressure should not exceed 40 psi:

  • engine running at 1,500 rpm
  • A/C switch ON
  • blower speed set to "HI"
  • temp setting at "MAX COOL"
  • air inlet setting at "RECIRC"

Hope this helps.

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