DerBassSpieler
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New to the forum here, and hoping you all can help! Working on my buddy's 2002 Yukon SLT with front and rear AC system.
TLDR: I think the front evaporator is clogged - what do you think?
Initally, AC system had barely any pressure in it (~5-10psi). I added a little r134a and found the low-side port was leaking (put a little fluid on top and watched bubbles slowly form). I also found that the compressor coud spin freely (no signs of failed compressor). Of course, there could be bigger issues, but I proceeded anyway.
I swapped out the ports (both) and accumulator with no issue. I pulled the front orifice tube out - there was nothing caught in the filter. I replaced it anyway. Here's a small thing (may not even be an issue). The original orifice tube was a fixed-type, I replaced it with the adjustable type (UAC EX5378C). It did not initially slide in easily. I had to lube it, then force it. I realized that I may have had it aligned such that the filter was fighting with the retaining dimples on the hard line (the one that it fits into). If I had rotated it a bit, it probably would have slid in easier.
Anyway, tightened everything up, then vacuumed it down to about -30 inHg for 45 minutes. Left it alone for another 45, and it didn't lose any vacuum. I preliminarily trust that there are no obvious leaks in the system.
Now on to filling: Because I evacuated the system and also replaced the accumulator, I should be adding about 2oz PAG oil and 48oz of r134a (as specified on the sticker in the engine compartment). I start it up, and put the FRONT (should have put back on too, my bad) AC controls on the coldest setting and the fan on AUTO, recirculation and AC buttons on (lit up). First, I added the 2oz oil through my gauges. Then, I started adding my first can of r134a. As you might expect, the compressor turned on occasionally, until one of the pressure cut-off circuits turn it back off.
I did this for all 48oz, but surprisingly, the vents never put out cold air. The low pressure side of the front orifice tube (between high and low ports) got super cold, and the high pressure side stayed warm. The pressures never got to their correct levels, but that's because the compressor never stayed on long enough for it to happen. It was getting late, so I quit for the night, a little bit unsure what was happening.
Next day I think to myself, "Wait, what about the rear AC circuit?" Sure enough, when I turn front and rear on (coldest temp setting, everything on AUTO), the rear AC puts out ice cold air (about 30-40 degrees cooler than ambient air) but the front is still warm. So at least now I know the compressor is good, the condenser is good, and the refrigerant is at least nearly correct.
Just in case there's a blockage at the air intake or something, I opened the filter housing and replaced the filters (they weren't too bad).
Now for some measurements: With the system off, the static pressure is about 95 PSI. If I turn on the full AC system to max (front and back), the system initially goes to 35 PSI low side, 150 PSI high side. Since its about 80-85 F out, the pressures should be about 50 and 220 PSI. Here's the weird thing: after about a minute, the low side goes to 30 and the high side goes to 275. At this time, the rear system is super cold, but the front is just ambient temp. The low side between the front orifice tube and front evaporator is also super cold. If I check the front evaporator (through the filter replacement opening), it's just a little cool though. I am detecting no leaks anywhere.
Here are the thing I'm thinking:
1. Am I just low on r134a? I put the exact amount specified in the system (though I could have lost some during can exchanges or something).
2. Did I damage the front orifice tube? I did force it when I put it in, but doesn't the temp difference before and after it mean it's functioning? Also, the low side tubing to the evaporator measures about 45F, now icing externally.
3. Is the front evaporator clogged? I would think the result would be low pressure on the low side and high pressure on the high side, as I observed.
4. Might the system be icing up at the front evaporator?
Okay, I know this was way too detailed, but I'm hoping that someone can help. I'm not used to these two-loop systems! I suppose back AC is still better than no AC... Thanks everyone! -Steve
TLDR: I think the front evaporator is clogged - what do you think?
Initally, AC system had barely any pressure in it (~5-10psi). I added a little r134a and found the low-side port was leaking (put a little fluid on top and watched bubbles slowly form). I also found that the compressor coud spin freely (no signs of failed compressor). Of course, there could be bigger issues, but I proceeded anyway.
I swapped out the ports (both) and accumulator with no issue. I pulled the front orifice tube out - there was nothing caught in the filter. I replaced it anyway. Here's a small thing (may not even be an issue). The original orifice tube was a fixed-type, I replaced it with the adjustable type (UAC EX5378C). It did not initially slide in easily. I had to lube it, then force it. I realized that I may have had it aligned such that the filter was fighting with the retaining dimples on the hard line (the one that it fits into). If I had rotated it a bit, it probably would have slid in easier.
Anyway, tightened everything up, then vacuumed it down to about -30 inHg for 45 minutes. Left it alone for another 45, and it didn't lose any vacuum. I preliminarily trust that there are no obvious leaks in the system.
Now on to filling: Because I evacuated the system and also replaced the accumulator, I should be adding about 2oz PAG oil and 48oz of r134a (as specified on the sticker in the engine compartment). I start it up, and put the FRONT (should have put back on too, my bad) AC controls on the coldest setting and the fan on AUTO, recirculation and AC buttons on (lit up). First, I added the 2oz oil through my gauges. Then, I started adding my first can of r134a. As you might expect, the compressor turned on occasionally, until one of the pressure cut-off circuits turn it back off.
I did this for all 48oz, but surprisingly, the vents never put out cold air. The low pressure side of the front orifice tube (between high and low ports) got super cold, and the high pressure side stayed warm. The pressures never got to their correct levels, but that's because the compressor never stayed on long enough for it to happen. It was getting late, so I quit for the night, a little bit unsure what was happening.
Next day I think to myself, "Wait, what about the rear AC circuit?" Sure enough, when I turn front and rear on (coldest temp setting, everything on AUTO), the rear AC puts out ice cold air (about 30-40 degrees cooler than ambient air) but the front is still warm. So at least now I know the compressor is good, the condenser is good, and the refrigerant is at least nearly correct.
Just in case there's a blockage at the air intake or something, I opened the filter housing and replaced the filters (they weren't too bad).
Now for some measurements: With the system off, the static pressure is about 95 PSI. If I turn on the full AC system to max (front and back), the system initially goes to 35 PSI low side, 150 PSI high side. Since its about 80-85 F out, the pressures should be about 50 and 220 PSI. Here's the weird thing: after about a minute, the low side goes to 30 and the high side goes to 275. At this time, the rear system is super cold, but the front is just ambient temp. The low side between the front orifice tube and front evaporator is also super cold. If I check the front evaporator (through the filter replacement opening), it's just a little cool though. I am detecting no leaks anywhere.
Here are the thing I'm thinking:
1. Am I just low on r134a? I put the exact amount specified in the system (though I could have lost some during can exchanges or something).
2. Did I damage the front orifice tube? I did force it when I put it in, but doesn't the temp difference before and after it mean it's functioning? Also, the low side tubing to the evaporator measures about 45F, now icing externally.
3. Is the front evaporator clogged? I would think the result would be low pressure on the low side and high pressure on the high side, as I observed.
4. Might the system be icing up at the front evaporator?
Okay, I know this was way too detailed, but I'm hoping that someone can help. I'm not used to these two-loop systems! I suppose back AC is still better than no AC... Thanks everyone! -Steve
