Auto Ac Orifice Tube Location

Auto AC Orifice Tube Operation

An orifice tube is similar to an expansion valve, with both performing an important function in a vehicle’s A/C system. The valve helps control the flow of refrigerant through the evaporator, which is the main cooling component of the system. An expansion valve controls this flow directly through a modulating rod, which opens and closes.

How does an automotive AC orifice tube system work

Some car makers now use automotive AC orifice tube systems in their AC. An orifice tube is simply a refrigerant metering device to control the rate of flow of refrigerant into the evaporator located in your dash. In the illustration below, you’ll see that low pressure gas flows out of the evaporator coil and into the accumulator. A low pressure switch is often located right on the accumulator or in the low pressure line before the compressor. The low pressure switch is used to control when the compressor clutch engages and disengages. As the temperature of the refrigerant gas drops, so does it’s pressure and the switch turns off the compressor clutch. As cabin air blows across the evaporator, the gas heats and raises temperature and pressure and the switch then operates the compressor clutch again. It’s really that simple.

Refrigerant flow through the system

When the AC compressor engages, it sucks low pressure refrigerant gas from the evaporator and accumulator. The compressor then compresses the gas into a higher pressure and forces it into the condenser. During the compression cycle, the gas rises in temperature. Airflow across the condenser cools the high pressure gas, causing it to condense into a high pressure liquid.

The high pressure refrigerant flows to the screen and port in the orifice tube. Once the high pressure liquid passes through the orifice, the liquid pressure drops and the liquid begins to fill the evaporator. Airflow across the evaporator causes the liquid refrigerant to boil and turn into a gas again. The amount of heat it takes to change the refrigerant from liquid to gas is what an AC system removes from your car.

An orifice tube is an expansion device that controls refrigerant volume in front of the A/C evaporator. This tube prevents your evaporator from freezing. Unlike an expansion valve, an orifice tube is not adjustable. Other parts work with the orifice tube to regulate volume as the compressor cycles on and off as needed.
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Where is the orifice tube located?

Orifice tubes are always located in the refrigerant tubing that connects to the high pressure port on the evaporator. However, the tube may be located in the evaporator tubing itself.

In either designed, you must evacuate the system and disconnect the high pressure line from the evaporator to replace the orifice tube. If the screen is clogged, the entire system must be flushed and components replaced. The accumulation of debris caused by Black death, or the failure of a major components, cannot be flushed out of the condenser or evaporator. Those components must be replaced to restore proper AC operation.

AC orifice tube system

What goes wrong with an orifice tube?

Orifice tubes fail due to a clogged screen. The clog is caused by oil deterioration due to a low oil condition, acid formation in the system due to excess moisture or metal particles from component failure (also known as black death).

New and clogged AC orifice tube. Clogged tube shows evidence of “Black Death.”

Posted on by Rick Muscoplat

location of orifice tube on 99 chevy suburban

GEB on Mon April 24, 2006 3:34 PM

Year: 1999
Make: chevy
Model: suburban
Engine Size: 5.7l
Refrigerant Type: 134

I'm having trouble locating the orifice tube on this system/ dual air thanks

Chick on Mon April 24, 2006 3:47 PM

Dual air it should be right before the split to the rear line, or just after it towards the evaporator (High side) hope this helps.
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Chick
Email: Chick
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Freedoms just another word for nothing left to lose
Edited: Mon April 24, 2006 at 3:48 PM by Chick

Ac Orifice Tube Direction Diagram

chris142 on Wed May 17, 2006 9:33 PM

If I remember correctly it's in the connection under the air filter. Easiest to get to after removing the air filter assembly.

mickeycool17 on Sun July 16, 2006 9:30 PM

just got done working on a 99 chevy suburban. the orifice tube is in thr high side line of the front evaperator,it the lower line as you face the firewall. take off the window washer jug. the small line. but be very careful trying to undo thr fitting its tight.use 2 wrenches. dont slip cause if you do you coukd wipe out the evaporator lines and the heater core lines right below! that would be a pisser we gave up cause once we broke the connection loose it became very hard to turn the fitting. any suggestions?
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geturdone

Chick on Sun July 16, 2006 9:53 PM

Air Conditioning Orifice Tube Location

When you reassemble it, a 'drop' of nylog on the threads will help it go back on easy...Not just for O rings...
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Chick
Email: Chick
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Freedoms just another word for nothing left to lose

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