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2002 Subaru Outback LL Bean H6
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Discussion Starter #1
So my first 80 degree day of the year I went to turn on my A/C and got nothing. After some some investigating found the relay was bad. After replacing the relay, the compressor turned on as it was supposed to and attached my newly acquired manifold gauge set to check the pressures the right way. And noticed the low side was under the desired range and the high side was at the upper limits, (30L/170H) at 75 degrees. Which points to a clogged or clogging expansion valve which I already have along with a new receiver drier.

Question is if I collect the refrigerant, replace the drier and expansion valve. Pull a vacuum and refill with the cans of R134A, how do I know I don’t have too much oil in the system. The cans will add oil to the system and the system has oil already in it. From research too much oil will prevent the compressor from functioning.

Does it need to be flushed first or am I in the clear? Am I limited as a DIYer and need to give up and pay someone a ton of $$$ or is there something else I should do.
@idosubaru and anybody else have any input?


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I don't think that you have a clogged expansion valve at all. In fact those pressures look fairly normal to me. Is it cooling fine? What is the temperate of the suction line coming back to the compressor? Does it feel cold to the touch?
 

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Discussion Starter #3
I don't think that you have a clogged expansion valve at all. Is it cooling fine? What is the temperate of the suction line coming back to the compressor?


It’s cooling but not very cold, haven’t checked the temps but it is working. Had read the literature that came with the gauge and said a low low and a high high was indicative of an expansion valve. Just checked the low and high lines, the low is cold and the high is warm.


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Those are great pressures. If convert them to temperature, that says your evaporator is around 34 degrees and your condenser is around 120 degrees. The fact that the suction line is cold tells me that your evaporator is getting plenty of refrigerant. It seems from what you have described the refrigerant portion may be working correctly

Do you have a way to check the vent temperature at the center vent?
 

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The trouble with using a generic pressure, is the system is very dynamic based on load and temperature. Even a change in humidity changes the load on the system and makes some changes to the values.
 

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Discussion Starter #6
I hope to invest in a infrared thermometer but could buy a cheep cooking thermometer to check for now. Problem is it’s 51 degrees out so don’t know if that’ll skew the readings.



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Discussion Starter #7
The cars A/C system has almost 280k on it and as far as I know, it was all OEM, which is the Reason I already had the expansion valve and receiver drier. Last year I had a leak and had to replace the O-Rings on the compressor. Afterwards the system was intermittent but had used the cheap gauge that comes with the cans at the auto parts store, so couldn’t check the pressures properly. Guess the relay was already going bad.


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I actually prefer a regular thermometer. Similar to this. For some reason, I don't seem to get a good reading on vent temperatures with an infrared thermometer.
 

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Discussion Starter #9
Easily done, would the cold outside temps skew the readings. When it was 75 and sunny it didn’t feel all that cold but today being 51 and rainy it did feel colder. Should I wait for the next warm day?


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Easily done, would the cold outside temps skew the readings. When it was 75 and sunny it didn’t feel all that cold but today being 51 and rainy it did feel colder. Should I wait for the next warm day?
Yes, having a warm day is much better for checking A/C systems.
 

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Discussion Starter #11
That’s what I thought, though the forecast doesn’t look like it’s gonna cooperate


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Putting your hand on the suction line going to the compressor is a very good way to tell how the system is performing. That is always my first step.

45 and rainy here... time for winter to be over...
 

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Discussion Starter #13
When you say the suction line, the line between the condenser to the pump? So should be ice cold right?


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It is the larger line from the evaporator to the compressor. That is the outlet from the evaporator. Its temperature is directly related to the evaporator temperature. Cold evaporator = cool car... :)

If its sweating ... that is very good..
 

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Discussion Starter #16
It’s pretty cold to the touch and sweating but humidity is high with the rain and a high of only 53 today


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Discussion Starter #18
Central Kentucky, just for shits and giggles I went and purchased a thermometer. With the outside temp around 52, humidity around 90 the gauge is reading around 49 from the left center vent.




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For some reason, I don't seem to get a good reading on vent temperatures with an infrared thermometer.
Much like your own eyes, an infrared thermometer can't see the air. Therefore it can't read the air's temperature. Instead, the tool is telling you the temperature of what it can see, which would generally be a plastic vent face or ductwork in this application. The insulating properties of plastic makes for extremely lagged readings versus a traditional conductive metal probe thermometer.
 

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Central Kentucky, just for shits and giggles I went and purchased a thermometer. With the outside temp around 52, humidity around 90 the gauge is reading around 49 from the left center vent.
Just to make sure I'm tracking this right, you had the system open last year for new o-rings, then refilled it with oneshot store cans? Did you pull a vacuum on the system before filling it? A mix of air and refrigerant does allow the system to work, but it also explains some lost efficiency.
 
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