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Classification: Reference: Date:

HA93-001 NTB93-001 December 1992

A/C SYSTEM CHANGES FOR R-134A REFRIGERANTAPPLIED VEHICLE(S): All Models

SERVICE INFORMATIONTable Of Contents

Section I - General Information

Introduction...................................................................................................................... 2

Refrigeration handling precautions .................................................................................. 2

Refrigerant terminology .................................................................................................. 3

A/C system refrigerant & lubricant .................................................................................. 4

A/C system components ................................................................................................. 8

Service tools & equipment .............................................................................................. 15

Service procedures ......................................................................................................... 20

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IntroductionDue to its harmful effect on the stratospheric ozone layer, R-12 will be phased out andreplaced by R-134a, which does not harm the ozone layer. While the R-134a A/C systemis very similar to an R-12 A/C system, the differences in the refrigerant, lubricant andservice equipment are significant.

Nissan A/C systems may change from R-12 to R-134a at the time of new vehicle (fullmodel change) introduction, or in some cases by model year update to an existing modelline.

Section I of this bulletin describes all of the general differences between the R-12 and R-134a systems. Section II of this bulletin describes the details of the R-134a systems foreach of the specified models to which R-134a has been applied.

Refrigerant Handling Precautions• R-12 refrigerant and R-134a refrigerant must never be mixed, even in the smallest

amounts, as they are incompatible with each other. If the refrigerants are mixed,compressor failure is likely to occur.

• Use only specified lubricant for the R-134a A/C system and R-134a components.If lubricants other than those specified are used, compressor failure is likely tooccur.

• The specified R-134a lubricant absorbs moisture from the atmosphere at a rapid rate,therefore the following handling precautions must be observed:

• When removing refrigerant components from a vehicle, immediately cap (seal) thecomponent to minimize the entry of moisture from the atmosphere.

• When installing refrigerant components to a vehicle, do not remove the caps(unseal) until just before connecting the components. Also, complete the connectionof all refrigerant tubes and hoses without delay to minimize the entry of moisture intothe system.

• Use the specified lubricant from a sealed container only. Containers must be re-sealed immediately after dispensing the lubricant. Lubricant in containers which arenot properly sealed will become moisture saturated. Such lubricant is no longersuitable for use and should be properly disposed.

• Avoid breathing A/C refrigerant and lubricant vapor or mist. Exposure mayirritate eyes, nose and throat. Use only approved service equipment meeting SAEstandards to discharge R-134a systems.

• If accidental system discharge occurs, ventilate the work area before resumingservice.

• Always wear eye and hand protection (goggles and gloves) when working withany refrigerant or air conditioning system.

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• Do not store or heat refrigerant containers above 125°°°°F (52°°°°C).

• Do not heat a refrigerant with an open flame; if container warming is required,place the bottom of the container in a pail of warm water.

• Do not intentionally drop, puncture or incinerate refrigerant containers.

• Keep refrigerant away from open flames: hazardous gas will be produced ifrefrigerant is exposed to an open flame.

• Refrigerant will displace oxygen, therefore be certain to work in well-ventilatedareas to prevent suffocation.

• Do not introduce compressed air to any refrigerant container or refrigerantcomponent, because contamination will occur.

• R-134a in the presence of oxygen and under pressure may form a combustiblemixture. Therefore, never introduce compressed air into any R-134a container,cylinder A/C component, recover/recycle equipment, or other service equipment.This includes "empty" containers

Refrigerant TerminologyPlease use the correct name or names when specifying refrigerants. The guidelines arelisted below:

• Freon® is a registered trademark of DuPont, and should only be used if referring toDuPont R-12.

• DuPont's trade name for R-134a (automotive use) is Suva® Trans A/C.

• When referring to refrigerants, the terms Freon® and Suva® should not be used as ageneral reference. The proper terms are R-12 and R-134a.

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Comments regarding refrigerants:• R-12 and R-134a are not compatible with each other and should never be mixed,

even in the smallest amounts.

• R-134a for automotive use has a special tank fitting size (1/2" - 16 ACME) which iscompatible with automotive service equipment. DO NOT purchase or acquire R-134a incontainers with 1/4" flare fittings, as this will lead to cross contamination of A/C systemsand/or service equipment.

• When purchasing R-134a, be certain that the fitting size on the tank is 1/2" - 16 ACME.This thread size is easy to recognize by the square thread, as shown below.

• Although R-134a has no ozone depletion potential (ODP), it does have a slight globalwarming potential (GWP). Due to this slight GWP, as well as its high cost, venting of R-134a into the air is not recommended.

• Recovery/recycling of R-134a will be required by U.S. Federal Law, Clean Air ActAmendments of 1990.

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Comments regarding PAG refrigerant oils:• PAG oil absorbs moisture from the air at an exceptionally fast rate, and moisture can

damage the A/C system.

• The graph on the following page shows that PAG oil left open to air (e.g. in an unsealedcontainer) will absorb 2% moisture (by weight) in 120 hours (5 days).

• PAG containers, and any A/C component which contains PAG oil (such as thecompressor) should remain tightly capped and sealed until ready for use.

• If you believe that a container of PAG oil may not have been adequately re-sealed afteropening, dispose of the oil properly and use oil from a new sealed container.

• The figure below shows the re-useable plastic seal for the containers of Nissan A/CSystem Oil; be certain to use them when re-sealing these containers.

• When installing or servicing an A/C system, the refrigerant tube and hose connectionsshould be sealed (all connections made and tightened to specification) without delay.

• The above precautions will keep the absorption of moisture into the system to aminimum.

• Using moisture saturated PAG oil in R-134a systems may lead to the formation of acidsand related system damage or failure.

• Do not allow refrigerant oil (Nissan A/C System Oil) to contact styrofoam, as thelubricant will damage this material.

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This graph shows moisture absorption characteristics of Nissan A/C System Oil (Type R)with ambient temperature of 77°F (25°C) and relative humidity of 85%.

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Comments regarding liquid tanks:• For R-134a, the sight glass has been deleted. Refer to the service procedures section

of this bulletin for additional information regarding the refrigerant charge determination.

• Neither liquid tanks nor pressure switches are interchangeable between R-12 and R-134a systems.

• The tube flange locating pin (located on the tubes connecting to the liquid tank), and thecorresponding pin hole on the liquid tank have been changed for R-134a, as shown inthe detail views above.

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R-134a Service Tools & Equipment• R-12 and R-134a require separate and non-interchangeable sets of recovery,

recycle, and recharge equipment, because the refrigerants and lubricants are notcompatible and cannot be mixed even in the smallest amounts.

• DO NOT attempt to use one set of equipment for both R-12 and R-134a, as allequipment contains residual amounts of refrigerant and/or lubricant, which willresult in contamination, and damage to recovery/recycle equipment.

• Use equipment designed to meet Society of Automotive Engineers (SAE) standards,which specify R-134a service equipment fitting size (1/2" -16 ACME), and service hoseidentification (black stripe on hose).

• Adaptors to convert from one size fitting to the other must never be used;refrigerant/lubricant contamination will occur and system failure may result.

• The use of incorrect equipment will result in refrigerant and/or lubricant contamination,which may cause A/C system or equipment failure.

• The ACR4 machine will perform all required service functions (recovery, evacuation,recycle, recharge) on all R-134a vehicle systems.

• High volume A/C service facilities may benefit from "component" A/C service equipment(vacuum pump, weight scale, manifold gauge set) or separate charging systems tosupplement the ACR4 machine.

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Comments regarding recovery/recycling equipment:

• Be certain to follow the manufacturer's instructions for machine operation and machinemaintenance.

• Never introduce any refrigerant other than that specified into the machine.

• Only R-134a containers with a 1/2" - 16 Acme can be used to add R -134a to the ACR4recovery/recycle machine.

• Periodic maintenance of this equipment is required; follow the manufacturer'srecommendations as described in the equipment instruction manual.

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Comments regarding R-134a manifold gauge set:• Be certain that the gauge face indicates R-134a or 134a.

• Be certain that the manifold gauge set has the 1/2" - 16 ACME threaded connections forservice hoses, ensuring that only R-134a service hoses are used.

• Be certain that no refrigerants other than R-134a (along with only specified lubricants)are used with the manifold gauge set.

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Comments regarding vacuum pump use:

• The lubricant contained inside the vacuum pump is not compatible with the lubricant forR-134a A/C systems.

• The vent side of the vacuum pump is exposed to atmospheric pressure, causing thevacuum pump lubricant to migrate out of the pump into the service hose if the pump isswitched off after evacuation (vacuuming) and there is no shut off valve between thepump and the hose.

• To prevent the migration of vacuum pump lubricant into service hoses, it is necessary touse a valve (which can be manually opened or closed) near the connection of theservice hose to the pump.

• On a vacuum pump which is equipped with an isolation valve (usually part of thevacuum pump), closing this valve will isolate the service hose from the pump.

• For pumps without an isolation valve, be certain that the service hose is equipped with amanual shut off valve near the pump end of the hose.

• Hoses which contain an automatic shut off valve at the end of the service hose must bedisconnected from the vacuum pump to prevent the migration of lubricant; as long asthe hose is connected, the valve is open and lubricant may migrate (with pump off).

• One-way valves which open when vacuum is applied and close under a no vacuumcondition are not recommended, because this valve may restrict the pump's ability topull a deep vacuum.

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Comments regarding leak detector use:

• Existing R-12 leak detectors currently will not detect R-134a.

• Many R-134a leak detectors will detect R-12; check with the equipment manufacturer.

• Always refer to and follow the equipment manufacturers recommendations whenoperating leak detectors.

Comments regarding weight scale use:

• If the scale allows electronic control of the flow of refrigerant through the scale, (i.e.internal solenoid valves) be certain that the hose fitting size is 1/2" - 16 ACME, and thatno refrigerant other than R-134a (along with only specified lubricant) have been usedwith the scale.

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Charging Cylinder• The use of a charging cylinder is not recommended because:

• The refrigerant may be vented into the air from the top of the cylinder when filling thecylinder with refrigerant.

• The accuracy of a charging cylinder is generally less than that of an electronic scaleor of quality recycle/recharge equipment.

Service ProceduresThe service procedures for R-134a A/C systems are basically the same as for the R-12 A/Csystems, however, the following should always be kept in mind:

• Avoid breathing A/C refrigerant and lubricant vapor or mist. Exposure mayirritate eyes, nose and throat. Use only approved recovery/recycling equipmentto discharge R-134a systems.

• If accidental system discharge occurs, ventilate the work area before resumingservice work.

• R-12 and R-134a require separate and non-interchangeable sets of recovery, recycleand recharge equipment, because the refrigerants and lubricants are not compatibleand cannot be mixed even in the smallest amounts.

• When leak checking an R-134a system, be certain that you are using a detector whichwill detect R-134a. Refer to page 18 for additional information.

• With R-134a systems it is especially important to properly control the amount ofrefrigeration charged into the system during system charging. A charging machine orweight scale must always be used during charging for proper charge determination.

• R-134a and R-12 A/C components are not interchangeable. Cleaning of used (inservice) components for use with another type of refrigerant and/or lubricant is not anacceptable practice, and may result in A/C system failure.

• Always use the proper PAG oil when servicing an R-134a A/C system. The Nissan partnumber for the appropriate PAG oil can be found on the A/C specification label in theengine compartment, and also in the Factory Service Manual, and on the label on thecompressor. These oils are only available from your Nissan Parts Department.

• As mentioned previously in this bulletin, the R-134a PAG lubricants absorb moisture;PAG oil containers and A/C components containing PAG oil must remain tightly sealeduntil ready for use.

• Unlike R-12 systems, R-134a systems do not exhibit a "clear sight glass" evenwhen properly charged. For this reason, the R-134a A/C systems have not sightglass.

• A recent SAE/MACS publication "Automotive Air-Conditioning Refrigerant ServiceGuide" contains practical information regarding legal and safe service procedures forboth R-12 and R-134a refrigerants. The publication is available from either SAE (412-776-4790) or MACS (215-541-4500).

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Questions regarding R-12 or R-134a should be addressed to your Regional TechnicalTraining Center or the FIXS Hotline.

Section II - Model Specific InformationFor additional information regarding model specific information, refer to the appropriateTechnical Service Bulletins listed below:

• 1993 D21/WD21 Truck/Pathfinder (Originally issued as Technical Service BulletinNTB92-055)

• 1993 U13 Altima (Originally found in 1993 Quest/Altima Product Bulletin)

• 1993 J30 Maxima (Originally issued as Technical Service Bulletin NTB92-059)

NOTE: As other Nissan models convert to R-134a, model specific information for eachmodel will be issued via Nissan Technical Service Bulletins.