Is the orifice tube on the low side or high side?
The orifice tube sits on the high-pressure side of the automotive air-conditioning system, located between the condenser and the evaporator, where it provides a fixed restriction to drop pressure before the refrigerant enters the evaporator.
In automotive A/C design, refrigerant leaves the compressor as a high‑pressure gas, is cooled and condensed into a high‑pressure liquid in the condenser, and then travels through the receiver/drier toward the expansion device. The orifice tube acts as the metering device that reduces pressure as the refrigerant flows into the evaporator, where it expands and absorbs heat before returning to the compressor via the low-pressure suction line.
Where the orifice tube sits in the system
The following points describe its placement and role within the typical fixed‑orifice A/C loop:
- Location: high-pressure side, in the liquid line between the condenser/receiver-drier and the evaporator.
- Device type: fixed‑orifice expansion device; some vehicles use a different expansion method (such as a thermostatic expansion valve or electronic expansion valve), but when an orifice tube is used, it is on the high side.
- Function: creates a substantial pressure drop across the device, metering refrigerant into the evaporator so it can expand and absorb heat.
- Relation to service ports: service ports are typically arranged with a high‑side port near the condenser and a low‑side port near the evaporator; the orifice tube itself sits upstream of the evaporator on the high side.
Understanding this placement helps technicians diagnose cooling problems, since a clogged or damaged orifice tube directly affects evaporator performance and overall system pressures.
Maintenance, diagnostics, and design variations
While the core idea is consistent, vehicle designs vary. Some modern vehicles use alternative expansion devices, which changes the exact location or integration of the metering component, but the principle of high‑side metering remains; if the system uses an orifice tube, it is still situated on the high-pressure side between the condenser and evaporator.
- Symptoms of a restricted orifice tube: reduced cooling capacity, especially at idle or in hot weather; elevated high-side pressure; sometimes an icing evaporator if flow is severely restricted.
- Diagnostic steps: compare high-side and low-side pressures under known loads, inspect orifice tube and related lines for debris or contamination, and consider replacing the receiver/drier and the orifice tube if contamination is suspected.
- Replacement considerations: use the correct metering device for the vehicle; ensure proper refrigerant type and oil charge; evacuate and recharge the system to factory specifications after replacement.
Note: Working on automotive A/C systems requires proper equipment and refrigerant handling. If in doubt, consult a qualified technician to ensure correct diagnosis and service.
Variations by design
Some vehicles employ a thermostatic expansion valve (TXV) or an electronic expansion valve (EXV) instead of a fixed orifice tube. In those systems, the metering device adapts to operating conditions; however, when an fixed orifice tube is used, the device remains on the high-pressure side, immediately before the evaporator.
Summary
For automotive air-conditioning systems that use an orifice tube, the device is located on the high-pressure side of the system, between the condenser and the evaporator. It functions as a fixed metering device that creates the necessary pressure drop to allow refrigerant to expand in the evaporator. Understanding this placement is essential for diagnosing cooling performance issues and planning maintenance, especially when verifying system pressures and replacing components like the receiver/drier or the metering device itself.
Which way does an orifice tube go in?
And as you know refrigerant flows out of the condenser. And comes along here and then it goes out this way. So when you go to put an orifice tube in you want to make sure it goes like this.
Is the orifice tube on the high side or low side?
Some systems are designed so that the orifice tube is mounted in the high side of the liquid refrigerant line in the evaporator. In some systems, the orifice tube can be mounted in the condenser outlet, which can soften the hissing noises that traditionally are produced when this type of A/C system is turned off.
Which line is the high side on an AC unit?
Blue so with that in mind. If you look at the line here on the right hand side where the red hose is connected to it. This is what is known as the high side.
Do you add freon to high side or low side?
low side
If hooking a can of refrigerant with a single hose/gauge to the car, you will use the low side.
