What makes you think the expansion valve has gone south?

If and when you open the system/repair, you'll have to 'evacuate' with a suction pump for at least 1 hour to remove all traces of moisture in the closed/sealed system. After that (with the vacuum steady & still on the system without changing), you'll have to add the freon until a stabilized low pressure is achieved. Using the correct gauges and the chart for the temperature/humidity, you'll add or substract freon (system running) until the system is correctly filled for the load calculated. Freon in the system never goes bad, if freon is again needed (later) at any time, you have a leak. Sometimes, small minor leaks can be sealed (one time only) with the correct system sealant, and then refilled again to it's normal capacity using the temperature/pressure chart for the system/time it is running (load). Backyard mechanics have shortcuts BUT these things sometimes cause other problems that wind up destroying/contaminating components like the compressor or system piping. Good luck!


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