Refrigerant pressure diagnosis

Working on an '07 Honda Civic LX sedan, auto, 43K miles. No cooling from AC. Static pressure is 125 PSI (it’s hot out). When the clutch engages, the compressor sounds fine, no ugly noises. The low side pressure drops to like 110-115 PSI, and the high side pressure drops slightly as well. Before deciding the expansion valve is bad, anything I should consider / try? Thanks!

That’s the component that controls the low side/high side pressures.

I would also suspect the expansion valve.


The compressor has failed, no surprise for a scroll type compressor. If the expansion valve were stuck open there would be some difference in low/high side pressures, just wouldn’t be effective.


Your pressures indicate a failed compressor, not an expansion valve.



Thanks. Two follow-up questions:

  1. What should be my next steps to verify it’s the compressor?
  2. What pressures would I expect to see if the expansion valve was stuck open?

Thanks again.

Change the expansion valve, it’s cheaper then the compresssor.

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I’d take to a pro and get it fixed once instead of maybe twice. Either repair requires evacuating and capturing the Freon-can you do that?

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With the compressor spinning, I clamped off the rubber hose on the low side. Made no change to pressures. Guess that does it for the compressor. Thanks for the heads up.

Before throwing a guess at the problem I would want to know where in the system the high and low pressure service ports are.

And pinching off an AC hose will likely damage it.


Alas, the black death is upon him. Finally got the new compressor and condenser, opened the system, and found this in the old compressor. I pulled the evaporator, ordering evaporator and expansion valve now.

Can the lines be flushed, or should I replace them too?

Flush the hoses and evaporator.


Both sides of the expansion valve are full of junk; no way am I reusing that evaporator.

I have ordered a flush kit for the lines.

You may find that it takes many hours to remove and replace that evaporator.

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First time pulling the evaporator, took like 45 min. Would probably take half that next time.

Reassembly will be a bit finicky, there are several deeply recessed fasteners.