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Hose and Lines

Hose and Lines

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High side / low side High side / low side

• System with an expansion valve• System with an expansion valve

High Side Low Side

Condenser Evaporator

Receiver/Drier

Compressor

Expansion valve

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High side / low side High side / low side

• Orifice tube system• Orifice tube system

High Side Low Side

Condenser EvaporatorAccumulator

Compressor

Orifice tube

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3 Lines3 Lines

• There are 3 lines in all automotive A/C systems:– Liquid line– Suction line– Discharge line

• There are 3 lines in all automotive A/C systems:– Liquid line– Suction line– Discharge line

Liquid line

Suction line

Discharge line

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Liquid lineLiquid line

• The liquid line caries high pressure liquid refrigerant from the condenser to the evaporator.

• The receiver drier, orifice tube or expansion valve is in series with the liquid line circuit.

• The liquid line caries high pressure liquid refrigerant from the condenser to the evaporator.

• The receiver drier, orifice tube or expansion valve is in series with the liquid line circuit.

Condenser outlet

Evaporator inlet

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Liquid lineLiquid line

• The liquid line can be made entirely of metal tubing if it is not attached to the sub-frame at any point.– Since the rubber sub-frame bushings

compress under suspension loads a liquid line that is attached at any point to the sub-frame needs sections of flexible rubber tubing at both ends.

• Of all the A/C lines the liquid line has the smallest inside diameter.

• The liquid line can be made entirely of metal tubing if it is not attached to the sub-frame at any point.– Since the rubber sub-frame bushings

compress under suspension loads a liquid line that is attached at any point to the sub-frame needs sections of flexible rubber tubing at both ends.

• Of all the A/C lines the liquid line has the smallest inside diameter.

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Suction lineSuction line

• The suction line connects the outlet of the evaporator to the compressor suction port.

• The suction line carries low pressure vapor so it has the largest diameter of all the lines.

• Since the compressor is mounted on the engine the suction line must have a section of flexible rubber hose to allow for engine torque reaction.

• In orifice tube systems the accumulator is in series with the suction line circuit.

• The suction line connects the outlet of the evaporator to the compressor suction port.

• The suction line carries low pressure vapor so it has the largest diameter of all the lines.

• Since the compressor is mounted on the engine the suction line must have a section of flexible rubber hose to allow for engine torque reaction.

• In orifice tube systems the accumulator is in series with the suction line circuit.

Compressor inlet Accumulator

outlet

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Discharge lineDischarge line

• The discharge line carries high pressure vapor from the compressor to the condenser.

• The discharge line also requires a section of flexible rubber.

• The discharge line is the mid size line – larger than the liquid line but smaller than the vapor line.

• The discharge line carries high pressure vapor from the compressor to the condenser.

• The discharge line also requires a section of flexible rubber.

• The discharge line is the mid size line – larger than the liquid line but smaller than the vapor line.

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MufflersMufflers

• A muffler is often installed in the line to dampen out pressure pulsations , which makes the system quieter.

• Piston type compressor produce pressure in waves of high and low pressure.

• A muffler is often installed in the line to dampen out pressure pulsations , which makes the system quieter.

• Piston type compressor produce pressure in waves of high and low pressure.

• The pressure wave can create pulsations in the lines that are attached to the body or the evaporator box that will be heard as a ‘pockety-pockety’ type noise.

• The pressure wave can create pulsations in the lines that are attached to the body or the evaporator box that will be heard as a ‘pockety-pockety’ type noise.

Muffler

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Hose assembliesHose assemblies

• When the hose ends of the suction line share a common flange with the discharge line the hoses assembly is replaced as a unit.

• If the damage is confined to just the rubber hose the assembly can often be repaired by a A/C specialty shop that has the specialized equipment needed to swag the new hose to the metal line.

• When the hose ends of the suction line share a common flange with the discharge line the hoses assembly is replaced as a unit.

• If the damage is confined to just the rubber hose the assembly can often be repaired by a A/C specialty shop that has the specialized equipment needed to swag the new hose to the metal line.

Flange

Muffler

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Rubber hosesRubber hoses

• The flexible rubber hoses used in the suction and discharge lines are made of synthetic rubber [ typically BUNA] and reinforced with woven polyester cord.

• R-134A systems require a nylon barrier layer between the liner and reinforcing layer.

• The outer layer may have a plastic coating to resist abrasion.

• The flexible rubber hoses used in the suction and discharge lines are made of synthetic rubber [ typically BUNA] and reinforced with woven polyester cord.

• R-134A systems require a nylon barrier layer between the liner and reinforcing layer.

• The outer layer may have a plastic coating to resist abrasion.

Image courtesy Goodyear Corp.

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Foam rubber and foil coveringsFoam rubber and foil coverings

• Foam rubber sleeves are often installed at points on the hose that may rub against other components.

• Foam rubber sleeves are often installed at points on the hose that may rub against other components.

• Hoses that run close to the exhaust manifold or turbocharger are covered with aluminum foil.

• Hoses that run close to the exhaust manifold or turbocharger are covered with aluminum foil.

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Hose permeabilityHose permeability

• Even with a barrier layer the rubber hoses in the A/C system are slightly permeable to water.

• Over a period of several years water can work it’s way through the rubber and past the nylon barrier where it is absorbed by the refrigerant.

• Water is a problem for two reasons.– Water will collect and freeze at the expansion

valve or orifice tube blocking the flow of refrigerant into the evaporator.

– Water chemically reacts with refrigerant to form acids that corrode the metal parts in the system

• Even with a barrier layer the rubber hoses in the A/C system are slightly permeable to water.

• Over a period of several years water can work it’s way through the rubber and past the nylon barrier where it is absorbed by the refrigerant.

• Water is a problem for two reasons.– Water will collect and freeze at the expansion

valve or orifice tube blocking the flow of refrigerant into the evaporator.

– Water chemically reacts with refrigerant to form acids that corrode the metal parts in the system

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Hose endHose end

• There are 3 common types of hose connection in use today.

– Flange– Threaded – Spring lock

• There are 3 common types of hose connection in use today.

– Flange– Threaded – Spring lock

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Flange type hose endsFlange type hose ends

• The hose end has a flat surface that connects to a corresponding flat surface on the compressor, accumulator or evaporator.

• Square cut or round o-rings are normally used to seal the connection.

• Components can be disconnected simply by removing a bolt.

• The hose end has a flat surface that connects to a corresponding flat surface on the compressor, accumulator or evaporator.

• Square cut or round o-rings are normally used to seal the connection.

• Components can be disconnected simply by removing a bolt.

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Threaded hose end connectorsThreaded hose end connectors

• The hose end is secured to the component by threaded aluminum nuts.

• A captive o-ring fits into a groove in the hose end.

• The male ends on the accumulator, evaporator or condenser often have flats so that two open end wrenches can be used to loosen and tighten the connector without damaging the component.

• The hose end is secured to the component by threaded aluminum nuts.

• A captive o-ring fits into a groove in the hose end.

• The male ends on the accumulator, evaporator or condenser often have flats so that two open end wrenches can be used to loosen and tighten the connector without damaging the component.

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Threaded connectorThreaded connector

• The o-ring seals against a step in the fixed connector end.

• This surface must be clean and free from nicks and scratches to ensure a tight seal.

• The o-ring seals against a step in the fixed connector end.

• This surface must be clean and free from nicks and scratches to ensure a tight seal.

Seal surface

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Removing threaded connectorsRemoving threaded connectors

• Hold the accumulator with a wrench to prevent damage when removing and installing hose connectors.

• Hold the accumulator with a wrench to prevent damage when removing and installing hose connectors.

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Spring lock connectorsSpring lock connectors

• Hoses with spring lock connectors are normally sealed with two or three captive o-rings at each end.

• A special spring expanding tool is needed to remove the hose ends.

• This type of connector is used by Ford and several European manufacturers.

• Hoses with spring lock connectors are normally sealed with two or three captive o-rings at each end.

• A special spring expanding tool is needed to remove the hose ends.

• This type of connector is used by Ford and several European manufacturers.

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Spring lock release tool setSpring lock release tool set

• The small connector tool [red] in this set is normally used for disconnecting fuel lines.

• The small connector tool [red] in this set is normally used for disconnecting fuel lines.

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Spring lock connectorSpring lock connector

• The female end of the spring lock connector is flared outward slightly.

• When the spring lock end is pushed on to the female tube end the spring expands and then snaps behind the flare – locking the two end together.

• When the connection is made the plastic collar snaps off of the spring lock indicating that a tight seal has been made.

• The female end of the spring lock connector is flared outward slightly.

• When the spring lock end is pushed on to the female tube end the spring expands and then snaps behind the flare – locking the two end together.

• When the connection is made the plastic collar snaps off of the spring lock indicating that a tight seal has been made.

Spring

Plastic collar

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Spring lock connectorSpring lock connector

• Inside the spring lock connector is a garter spring. A doughnut shaped coil spring.

• When the female end of the connector is pushed inward the garter spring expands and snaps over the bell mouthed end.

• The shape of the bell prevents the ends of the coupler pulling apart.

• Inside the spring lock connector is a garter spring. A doughnut shaped coil spring.

• When the female end of the connector is pushed inward the garter spring expands and snaps over the bell mouthed end.

• The shape of the bell prevents the ends of the coupler pulling apart.

Garter spring

O-ring

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Spring lock retaining clipSpring lock retaining clip

• A retaining clip is often installed to help hold the spring lock connection tight.

• A retaining clip is often installed to help hold the spring lock connection tight.

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O-ringsO-rings

• Most modern A/C systems use round cross section o-rings.

• Occasionally square cut o-rings are used on flange type connectors – typically when two hoses uses a common flange.

• O-rings used for R-12 systems are made of natural rubber [latex] or neoprene and a colored black.

• Most modern A/C systems use round cross section o-rings.

• Occasionally square cut o-rings are used on flange type connectors – typically when two hoses uses a common flange.

• O-rings used for R-12 systems are made of natural rubber [latex] or neoprene and a colored black.

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O-ringsO-rings

• R-134a systems use impervious neoprene [blue] or buna [green].

• Blue and green o-rings can be used on R-12 systems but black o-rings cannot be used on R-134a systems.

• R-134a systems use impervious neoprene [blue] or buna [green].

• Blue and green o-rings can be used on R-12 systems but black o-rings cannot be used on R-134a systems.