A clogged orifice tube blocks refrigerant flow into the evaporator. Symptoms include warm air despite a full charge, high pressure on the high side, and low pressure on the low side.
A compressor that has shed aluminum or steel debris sends it downstream. Particles lodge in the orifice tube screen and block refrigerant flow. Usually requires full system flush.
A saturated drier releases water into the system. Water plus refrigerant oil creates acids and sludge that plug the orifice tube.
Stop-leak products can clog the orifice tube. Common on cars that have had a DIY recharge with sealant included.
Old or contaminated oil thickens into sludge that blocks the tube. Less common with modern PAG oil but possible.
On new or recently serviced cars, residual debris from manufacture or repair can clog the tube. Rare but happens.
Mixing R134a with R1234yf or using an alternative refrigerant produces residues that plug the orifice. Full evac and proper refill required.
Water in the system freezes at the orifice and intermittently blocks flow. Symptoms come and go with run time.
| Likely Cause | Typical Cost | DIY Difficulty | Severity | Likelihood |
|---|---|---|---|---|
| Debris From Failed Compressor | $200-$600 orifice + flush | Hard | High | 70% |
| Moisture-Induced Corrosion Inside System | $200-$500 + new drier | Hard | Medium | 45% |
| Stop-Leak Sealant Residue | $300-$700 flush + parts | Hard | Medium | 35% |
| Aged Refrigerant Oil Sludge | $200-$500 + flush | Hard | Medium | 25% |
| Manufacturing Debris Left in System | $150-$400 replacement | Hard | Medium | 15% |
| Wrong Refrigerant Used | $300-$700 system service | Hard | Medium | 10% |
| Frozen Moisture Plug | $200-$400 + new drier | Hard | Low | 8% |
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A small fixed restriction in the AC system that meters refrigerant into the evaporator. Used on systems that do not have a thermal expansion valve (TXV). Acts like a tiny nozzle.
Warm air at the vents despite a full charge. Gauges show very high pressure on the high side (300+ PSI) and very low on the low side (under 20 PSI). Sometimes the inlet line to the evaporator gets icy while the outlet is warm.
On many cars yes. It is located in the high-pressure liquid line between the condenser and evaporator. You will need to discharge the system, replace the tube, and have it evacuated and recharged.
$200-$500 at a shop including the part, drier, evac, and recharge. The orifice tube itself is $10-$30.
Yes. Any time the system is opened to atmosphere, replace the drier. It absorbs moisture and you do not want a saturated drier in your fresh charge.
On a clean system, the life of the car. They typically fail because something else upstream failed and sent debris through.
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