2003 Audi A4 B6 3.0L 166k miles

Short Explanation: If you are opening up your AC system, consider using a standard fixed orifice tube versus the "variable orifice valve" (VOV) automatically adjusting orifice tube that is also available. I was thinking I might get improved cooling at idle but caused it to have no cooling at all.

More details:
I recently replaced the major components in my AC system, fully flushed lines and installed a new VOV automatic adjusting orifice tube (Four Seasons 38902, red <105°F). Pulled down to 29+ in. Hg for 2 hours. Held closed for 20 minutes with no leaks.

While weighing in the refrigerant charge, I initially had cold air blowing then it turned warm. By the time the full charge (19 oz + 0.7) was installed, gauges showed very low low side pressure (15 psig) and low high side (125 psig) at 83°F, 90% RH ambient. The inlet line to evaporator had heavy frost downstream of orifice tube…not normal. Outlet tube from evaporator to accumulator was warm. Supposedly there should only be about 5°F difference in temp between these two lines.

Orifice tube appeared to be the excessively high restriction point because that is where the frost accumulation began, just downstream. This is bad because it can starve the compressor of oil flow carried by the refrigerant which was clearly not flowing into the evaporator like it should.

I thought maybe I had installed the orifice tube backwards. Inspected that and it was clean and installed correctly. So I decided to get a OEM style, standard fixed orifice tube (38642) and install that, figuring keep it simple.

After pulling it down and charging, system works perfectly now. 33 low side, 185 high side, 83°F, 90% RH ambient, 43.5°F from air vents at idle speed.

I suppose I had a defective new “Smart VOV” orifice tube because I couldn’t find a lot of complaints about them in general. But, as I have learned so much from reading other posts over the years, I thought I would throw this one up there in case it might help someone with similar symptoms.