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chassis expansion txv conditioning tev air dryer thermostatic valve

Dash Air Thermostatic Expansion Valve
My dash air became inop because of a plugged thermostatic expansion valve. Classic symptoms were very low suction pressure and very high high side pressures with no cooling. Simple diagnosis but not so simple of a fix.

First challenge is to remove the old TXV. In my 99 it is in the bowels of the lower dash area. I finally gained limited access by removing both the HWH control panel and the rear view monitor. After evacuating the system, don't snigger I have a reclaim unit, I removed the TXV. The hunt was now on. No identifying info. It was made by Parker Hannifin, but they sold their automotive biz years ago. After two days of looking at expansion valve catalogs and surfing the interweb, the valve was identified. A Four Seasons 38872 is a workable replacement. You can get one here.

I also replaced the dryer, a rather generic part, but try getting one at the local parts house without a make model and year of car. I used this one  Four Seasons 33321.

I discovered a lot of debris at the filter dryer so I decided to flush the system. Holy moly, I got about a teaspoon, no exaggeration of grit out of the system. No wonder the TXV was stopped up. I suspect the original filter drier failed in some manner. 

Pulled a vac for a couple of hours, no leak down. Pumped up with N2 and no leak down. Put in 3.5 lbs of liquid R134a on the high side without the motor running. I let that sit for an hour. Then cranked the engine, and put in about another 8 oz of vapor on the low side. Ambient temp was 75. Low side was a steady 12 psi, and high was 175 psi. The gauges had never been this steady before. Vent temperature was frosty ! Oh yeah, I did put replacement PAG oil in for what I captured on the flush. 

Total refrigerant capacity for the system was very close to 4 lbs 134a. 

So, in addition to the part numbers. The primo lesson was if you tear into the dash air system, flush it, or you may be going back for rework soon. 

I will tweak the refrigerant level if necessary when the weather gets warmer. 

Hope this helps you someday.
Richard and Rhonda Entrekin
99 Newell, 512
Subaru Outback Toad
Inverness, FL (when we're home Cool )

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