HVAC System General Servicing. GMC Suburban I

USING R-12 & R-134a REFRIGERANT

Note. For additional A/C COMPRESSOR SERVICING information, see the A/C COMPRESSOR SERVICING article or the A/C COMPRESSOR REFRIGERANT OIL CHECKING article in the AIR CONDITIONING & HEAT section.

HANDLING/SAFETY PRECAUTIONS

1. Always work in a well-ventilated, clean area. Refrigerant (R-12 or R-134a) is colorless and invisible as a gas. Refrigerant is heavier than oxygen and will displace oxygen in a confined area. Avoid breathing refrigerant vapors. Exposure may irritate eyes, nose and throat.
2. Always wear eye protection when working around A/C system and refrigerant. The system's high pressure can cause severe injury to eyes and skin if a hose were to burst. If necessary, wear rubber gloves or other protective clothing.
3. Refrigerant evaporates quickly when exposed to atmosphere, freezing anything it contacts. If liquid refrigerant contacts eyes or skin (frostbite), DO NOT rub eyes or skin. Immediately flush affected area with cool water for 15 minutes and consult a doctor or hospital.
4. Never use R-134a in combination with compressed air for leak testing. Pressurized R-134a in the presence of oxygen (air concentrations greater than 60 percent by volume) may form a combustible mixture. DO NOT introduce compressed air into R-134a containers (full or empty), A/C system components, or service equipment.
5. DO NOT expose A/C system components to high temperatures (steam cleaning for example), as excessive heat will cause refrigerant system pressure to increase. Never expose refrigerant directly to open flame. If refrigerant needs to be warmed, place bottom of refrigerant tank in warm water. Water temperature MUST NOT exceed 125°F (52°C). CAUTION: When R-134a is exposed to an open flame, drawn into engine, or detected with a Halide (propane) leak tester, a poisonous gas is formed. Keep work areas well ventilated.
6. Use care when handling refrigerant containers. DO NOT drop, strike, puncture, or incinerate containers. Use Department Of Transportation (DOT) approved (DOT 4BW or DOT 4BA) refrigerant containers.
7. Never overfill refrigerant containers. The safe filling level of a refrigerant container MUST NOT exceed 60% of the container's gross weight rating. Store refrigerant containers at temperatures less than 125°F (52°C).
8. Freon (R-12) is sold and stored in White colored containers, while R-134a refrigerant is sold and stored in 30- or 50-pound Light Blue containers.
9. Refrigerant R-12 and R-134a must never be mixed, as they and their desiccants and lubricants are not compatible. If the refrigerants are mixed, system cross-contamination or A/C system component failure may occur. Always use separate servicing and refrigerant recovery/recycling equipment.
10. Read and follow equipment manufacturer's instructions for all service equipment to be used. The Material Safety Data Sheet (MSDS), provided by refrigerant manufacturer/supplier, contains valuable information regarding the safe handling of refrigerants.

IDENTIFYING R-134a SYSTEMS & COMPONENTS

To prevent refrigerant cross-contamination, use following methods to identify R-134a based systems and components.

Fittings & "O" Rings

All R-134a based A/C systems use 1/2" - 16 ACME threaded fittings (identifiable by square threads) and quick-connect service ports. (Scheme 5)

Scheme 5

REFRIGERANT OILS

Refrigerant R-12 based systems use mineral oil, while R-134a systems use synthetic Polyalkylene Glycol (PAG) oils. Using a mineral oil based lubricant with R-134a will result in A/C compressor failure due to lack of proper lubrication.

The following R-134a refrigerant oils are used by most domestic vehicles

GM

On all models except Saturn, use PAG Refrigerant Oil (Part No. 12345923). On Saturn, use Saturn PAG Refrigerant Oil.

Note. Use ONLY the specified oil for the appropriate system or A/C compressor. Always check the underhood A/C specification label or A/C compressor label before adding refrigerant oil to A/C compressor/system.

SIGHT GLASS INDICATOR

Note. Sight glass indicator conditions listed are for R-12 systems ONLY. R-134a systems may or may not have a sight glass.

Not all systems use a sight glass. If used, a sight glass may be mounted in receiver-drier or in discharge line. Refrigerant's condition can be visually checked while passing through sight glass. The following are possible conditions of sight glass indicator, which may help in the diagnosis of problems. (Scheme 6)

Note. Sight glass readings are not positive identification of a problem. Readings should be relied upon only when other system symptoms exist.

Clear Sight Glass

A clear sight glass indicates refrigerant level is correct or that the system has a complete lack of refrigerant, a condition accompanied by a lack of any cooling action by the evaporator. Sight glass may be clear, but system might be overcharged (too much refrigerant). This must be verified by test gauge readings.

Bubbly/Foamy Sight Glass

A bubbly or foamy sight glass indicates system is low on refrigerant, and air has probably entered system. Occasional bubbles during clutch cycling or system start-up may be okay.

Oil Streaked Sight Glass

If oil streaks appear on sight glass, a lack of refrigerant may be indicated, and the system's compressor oil is circulating through the system.

Cloudy Sight Glass

A cloudy sight glass indicates desiccant contained in receiver-drier or accumulator has broken down and is being circulated through system.

Identifying Sight Glass Indicator Conditions. Scheme 6

SCHRADER-TYPE VALVES

Note. Although similar in construction and operation to a tire valve, NEVER replace a Schrader-type valve with a tire valve.

Schrader valve is similar in construction and operation to a tire valve. (Scheme 7) When a test gauge hose is attached (hose has built-in valve core depressor), Schrader stem is pushed inward to the open position and allows system pressure to reach the gauge.

If test hose being used does not have a built-in core depressor, an adapter must be used. Never attach hoses or adapters to a Schrader valve unless it is first connected to manifold gauge set.

Schrader Service Valve (Compressor Location Shown). Scheme 7

SPECIAL VALVE CONNECTORS

On some General Motors models, thread size on high-side service valve (3/8" - 24 threads) is different from thread size on low-side service valve (7/16" - 20 threads). Special adapters are required to make this connection. (Scheme 8) These adapters are available in 45-degree and 90-degree angles in addition to straight-fixed and flexible adapters.

Flexible High Side Adapter. Scheme 8

R-134a SERVICE VALVES/PORTS

All vehicles with R-134a refrigerant use quick-disconnect service valves/ports. All R-134a systems use quick-disconnect fittings with sealing caps that thread into inside of service port instead of onto outside of service port.

The high side uses a large service port, and the low side uses a small service port. (Scheme 5) The R-134a service ports have internal metric threads to help prevent the accidental connection of R-12 servicing equipment.

There are 2 types of quick-disconnect service couplings which can be used on R-134a systems. One type of service coupling depresses service port valve when connection is made. The other type connects onto service port but will not depress service port valve until a knob is rotated. (Scheme 9)

Scheme 9

SERVICE VALVE LOCATIONS

For service valve locations, see SERVICE VALVE LOCATIONS (CARS) or SERVICE VALVE LOCATIONS (TRUCKS & VANS) table.

SERVICE VALVE LOCATIONS

SERVICE VALVE LOCATIONS

SERVICE EQUIPMENT

Because R-134a is not interchangeable with R-12, separate sets of hoses, gauges and recovery/recycling equipment are required to service vehicles. This is necessary to avoid cross-contamination and damaging system.

All equipment used to service systems using R-134a must meet SAE standard J1991. The service hoses on the manifold gauge set must have manual (turn wheel) or automatic back-flow valves at the service port connector ends. This will prevent refrigerant from being released into the atmosphere.

For identification purposes, R-134a service hoses must have a Black stripe along their length and be clearly labeled SAE J2196/134a. The low pressure test hose is Blue with a Black stripe. The high pressure test hose is Red with a Black stripe. The center test hose is Yellow with a Black stripe.

Note. Refrigerant R-12 service hoses will ONLY be labeled SAE J2196.

R-134a manifold gauge sets can be identified by one or all of the following

1. Labeled FOR USE WITH R-134a on set.
2. Labeled HFC-134 or R-134a on gauge face.
3. Light Blue color on gauge face.

In addition, pressure/temperature scales on R-134a gauge sets are different from R-12 manifold gauge sets.

MANIFOLD GAUGE SET

A manifold gauge set is used to determine system's high-side and low-side pressures, correct refrigerant charge, system diagnosis and operating efficiency. High (discharge) and low (suction) pressures must be compared to determine system operation. Manifold gauge sets for the 2 refrigerant types are basically the same except for fittings at ends of hoses. Fittings are different to ensure connection only to appropriate refrigerant system.

Low-Side Gauge

Low-side gauge, which may have a Blue identifying feature, is used to measure low-side (suction) pressure. Low-side gauge is also called a compound gauge because it can measure pressure and vacuum. Pressure scale ranges from 0 to 150 psi; vacuum scale ranges from 0 to 30 in. Hg.

High-Side Gauge

High-side gauge, which may have a Red identifying feature, is used to measure high-side (discharge) pressure. Gauge scale ranges from 0 to 500 psi.

CONNECTING GAUGE SET

Note. R-134a quick disconnect service couplings are connected in the same sequence as Schrader-type service valves.

1. Put on safety goggles, and cover vehicle's fender. Slowly remove protective caps from Schrader valves to check for leaky valves. CAUTION: Ensure hand valves on manifold gauge set and the hose-end shutoff valves are closed before attaching test hoses to Schrader valves.
2. Ensure service hoses are equipped with valve core depressor to match Schrader valve. If not, install special adapters for this purpose. If the high-side service hose connector will not fit on high-side Schrader valve, a special adapter must be used. See SPECIAL VALVE CONNECTORS.
3. Ensure both manifold gauge hand valves are closed. Connect low-side service hose to low-side (suction) service valve, and finger tighten connections. Connect high-side service hose to high-side (discharge) service valve, and finger tighten connections.

Note. After test gauges are installed, test hoses must be purged of all air before proceeding with testing.

PURGING TEST HOSES

1. Ensure high-side and low-side hoses are properly connected to service valves, and all hose connections are tight. Place a clean shop towel over end of center service hose.
2. Purge high-side test hose by opening hand valve on high-side gauge for 3-5 seconds. This allows system's refrigerant to force air through test hoses and out of center service hose into the shop towel. Immediately close high-side gauge hand valve.
3. Purge low-side test hose in the same manner using hand valve of low-side gauge. Close hand valve after 3-5 seconds. Purging of test hoses is now complete, and system is ready for testing.

Note. If manifold gauge set is to be used in conjunction with refrigerant recovery/recycling equipment, use instructions provided with the recovery/recycling equipment to properly purge test hoses.

STABILIZING A/C SYSTEM

1. Once manifold gauge set is attached to system and test hoses have been purged, system is ready for testing. Place all test hoses, gauge set and other equipment away from all moving parts of engine.
2. Start engine, and turn A/C controls to maximum cooling position (full cold or "MAX A/C"). Set blower fan on high speed. Open doors and/or windows. Operate system for 5-10 minutes. System should now be stabilized and ready for test readings.

PRESSURE-TEMPERATURE RELATIONSHIP

A refrigerant, when confined in an enclosed space, increases in pressure as the temperature increases. Conversely, if the temperature is lowered, the pressure also decreases.

Depending on temperature, a corresponding pressure will exist in a such an enclosed space. For example, at 70°F (21.1°C) a gauge will indicate about 71.0 psi (5.0 kg/cm 2 ). The R-134a PRESSURE-TEMPERATURE RELATIONSHIP table shows this relationship.

R-134a PRESSURE-TEMPERATURE RELATIONSHIP

PRESSURE GAUGE READINGS

The pressure gauge readings used represent an expansion valve type system using a Nippondenso 10-cylinder compressor. (Scheme 10)-14. Gauge indications will vary depending on system configuration and compressor application.

Temperature and humidity, as well as other factors, affect pressure gauge readings. Compared to R-12 systems, pressure readings on R-134a systems are generally lower for low-side pressure and higher for high-side pressure. Pressure gauge readings should be used only as a guide.

Note. For additional A/C COMPRESSOR SERVICING information, see the A/C COMPRESSOR SERVICING article or the A/C COMPRESSOR REFRIGERANT OIL CHECKING article in the AIR CONDITIONING & HEAT section.

Normally Functioning R-134a A/C System. Scheme 10

Some Moisture In R-134a System. Scheme 11

Low R-134a Charge. Scheme 12

Poor R-134a Refrigerant Circulation. Scheme 13

No R-134a Refrigerant Circulation. Scheme 14

Insufficient Cooling Of Condenser Or R-134a Refrigerant Overcharge. Scheme 15

Air In R-134a System. Scheme 16

Expansion Valve Improperly Mounted Or Heat Sensing Tube Defective (Opening Too Wide). Scheme 17

Compressor Malfunction. Scheme 18

ORIFICE TUBE REPLACEMENT

Note. Orifice tube is located in end of liquid line closest to component listed in ORIFICE TUBE LOCATION & REMOVER/INSTALLER APPLICATION table. Models not listed use a thermostatic expansion valve.

Removal

1. Locate orifice tube. See ORIFICE TUBE LOCATION & REMOVER/INSTALLER APPLICATION table. Discharge A/C system using approved recovery/recycling equipment. Disconnect liquid line at evaporator inlet. Remove orifice, and disconnect liquid line at evaporator or condenser.
2. Remove orifice tube using needle-nose pliers or orifice tube remover. See ORIFICE TUBE LOCATION & REMOVER/INSTALLER APPLICATION table.
3. If difficulty is encountered during removal of a plugged or restricted orifice tube, remove as much residue as possible. Using a heat gun, carefully heat inlet pipe. If inlet pipe has small dimples, apply heat1/4" from dimples. Be careful not to overheat pipe. NOTE: If system has a pressure switch near orifice tube location, remove switch before heating inlet pipe to avoid damaging switch.
4. While heat is being applied, install orifice tube extractor. Use a turning motion along with a push or pull motion to loosen and remove orifice tube.

Note. On some models, it may be necessary to use Dual "O" Ring Joint Separator (J-38042) to hold refrigerant line nut while loosening or tightening fitting.

Installation

1. To install orifice tube, coat inside of inlet pipe with refrigerant oil. Lubricate new orifice tube and "O" ring with refrigerant oil and insert them into inlet pipe.
2. Install orifice tube with shorter screen end first (toward evaporator). To complete installation, reverse removal procedure. Recharge and test system for proper operation.

ORIFICE TUBE LOCATION & REMOVER/INSTALLER APPLICATION

Scheme 19

REFRIGERANT RECOVERY/RECYCLING

Refrigerant recovery/recycling equipment is used to remove refrigerant from vehicle's A/C system without polluting atmosphere. To remove and recycle refrigerant, ALWAYS follow instructions provided with the refrigerant recovery/recycling equipment being used.

The removed refrigerant is filtered, dried and stored in a tank within the recovery/recycling equipment until it is ready to be pumped back into the vehicle's A/C system.

Note. Separate sets of hoses, gauges and refrigerant recovery/recycling equipment MUST be used for R-12 and R-134a systems. DO NOT mix R-12 and R-134a refrigerants, as their refrigerant oils and desiccants are NOT compatible.

1. Close both valves on manifold gauge set. Connect manifold gauge set to high-side and low-side service valves. See SERVICE VALVE LOCATIONS under SYSTEM SERVICE VALVES.
2. Connect center hose on manifold gauge set to inlet port on Refrigerant Recovery/Recycling Equipment (J-39500). Start engine. Turn A/C on for about 2 minutes. NOTE: Operating A/C for 2 minutes warms refrigerant, allowing greater recovery of refrigerant from system.
3. Shut engine off. Open both valves on manifold gauge set. Simultaneously open both valves on refrigerant recovery/recycling equipment storage tank.
4. Turn refrigerant recovery/recycling equipment on. Depress compressor START switch. Ensure the compressor ON light is activated.
5. The refrigerant recovery/recycling equipment will shut off when manifold gauge indicates vacuum reading of 17 in. Hg. Vacuum should remain at 17 in. Hg for at least 2 minutes.
6. Run recovery/recycling equipment one complete cycle. If vacuum reading is greater than zero after one complete cycle, some refrigerant still remains in vehicle's A/C system. Depress compressor START switch, and operate refrigerant recovery/recycling equipment through another cycle.
7. Once refrigerant is recovered, open accumulator pressure valve on the refrigerant recovery/recycling equipment for 15 seconds. This will pressurize the oil separator so refrigerant oil can be drained.
8. Open oil drain valve on refrigerant recovery/recycling equipment, and drain refrigerant oil into a container. Measure exact amount of oil to be added when system is put back in service.

FLUSHING A/C SYSTEM

1. Manufacturer does not recommend flushing A/C system. If system is contaminated, discharge system and install a liquid line filter between condenser and evaporator.
2. Filter may be an integral part of the line, or line may need to be cut and filter installed (non-integral type). Filters may or may not contain orifice. (Scheme 20)
3. Filter with orifice is installed on low pressure side of orifice tube. Remove original orifice tube if installing filter with orifice. Filter without orifice must be installed on high pressure side of orifice tube.
4. To install liquid line filter, discharge A/C system using approved recovery/recycling equipment. Remove liquid line. Using a tubing cutter, cut section from liquid line to allow installation of liquid line filter. Clean all burrs, and smooth surfaces.
5. Install nut over line. Install ferrule on line with small end toward nut. DO NOT install "O" ring at this time.
6. Push line into fitting until it bottoms on filter assembly. Tighten nuts on each joint to 11 ft. lbs. (15 N.m). Disassemble joint assembly.
7. Lubricate new "O" rings with refrigerant oil and install them on lines. Install filter assembly. Ensure arrow on filter indicates proper flow of refrigerant. Tighten nuts to 11 ft. lbs. (15 N.m). Evacuate and charge system. Check system for leaks.

Scheme 20

EVACUATING A/C SYSTEM

Information is not available from manufacturer.

CHARGING A/C SYSTEM

Note. Manufacturer does not recommend using one-pound cans. Using a charging station will allow precise measurement of refrigerant charge. See the REFRIGERANT OIL SPECIFICATIONS tables in the A/C COMPRESSOR SERVICING article for system capacities.

Note. DO NOT connect high-side gauge hose to high-side service port. Perform A/C charging service through low side only.

1. System must be evacuated before charging. With manifold gauge set connected (from evacuation procedure), start engine, but DO NOT turn on A/C. Connect refrigerant drum to hose on center connector of manifold gauge set. Invert refrigerant drum for liquid charging. Open low-side gauge valve on manifold gauge set. Allow 16 ounces of refrigerant to enter system.
2. When 16 ounces of refrigerant have entered system, turn A/C system to normal operating position with blower fan on high speed. Continue charging (liquid charging) until proper amount of refrigerant has entered system.
3. Close refrigerant drum valve, and continue running A/C system for 30 seconds to clear lines and gauges. Turn off valve on manifold gauge set. With engine running, disconnect low-side hose, and install service valve cap at accumulator. Perform leak test procedure. See LEAK TESTING.

Bubble Solution Detector

This is a solution applied externally at suspected leak points. Leaking refrigerant will cause the detector to form bubbles and foam. A soap and water solution also works well.

Dye Solution

This is a colored solution that may be introduced into the air conditioning system. The dye will show up and color components at leak points. Some manufacturers offer refrigerant containing a Red dye. This dye-containing refrigerant is installed by normal charging procedures. Other dye solutions are visible with a Black light only.

Electronic Detector

This instrument will draw in any leaking refrigerant through a test probe, and then sound an alarm or create a flashing light if refrigerant is found. It is the most sensitive of the leak detectors used. (Scheme 21)

Electronic Leak Detector. Scheme 21

PREPARATION FOR LEAK TESTING

Connect manifold gauge set to air conditioning system. Ensure low-side and high-side gauge set hand valves are closed. Check system pressure. It should be at least 50 psi (3.5 kg/cm 2 ). If low, add just enough refrigerant to bring system to 50 psi (3.5 kg/cm 2 ).

Ensure all joints, connections, and fittings are free of oil dirt and other contaminants. Using a refrigerant leak detector, check all refrigerant line connections for leaks. Check condenser and compressor seal area.

Refrigerants are heavier than air. Always check for leaks at bottom of refrigerant lines and components. Refrigerant oil will leak with refrigerant. Visually check all connections and compressor clutch area for oil stains. If compressor shaft seal is leaking, a fresh oil streak will normally be seen on underside of hood, above compressor clutch.

Always perform leak testing after A/C service. Move refrigerant leak detector slowly to check for leaks, as leaks will not be detected if leak testing is performed too quickly.

BUBBLE DETECTOR LEAK TESTING PROCEDURE

This leak detection method is recommended when it is impossible or difficult to determine the exact location of the leak using other methods. Although commercial bubble detectors are more effective, household soap solutions may be used.

Using the dauber that comes with the commercial soap solution, apply the solution to all joints, connections, fittings or controls where a leak might be suspected. If high-suds household solutions are used, apply them with a small brush. Wherever bubbles form, leaks are present and must be repaired. check the entire system as there may be more than one leak.

ELECTRONIC LEAK TESTING PROCEDURE

Note. Some electronic leak detectors will function on only R-12 systems or on only R-134a systems, and some will function on both R-12 and R-134a systems. Familiarize yourself with the test being used and know what type of system you are leak testing.

Electronic leak detectors should be used in well ventilated areas. Avoid using them around explosive gases. Always follow manufacturer's instructions for the specific tester being used. If none are available, proceed as follows

1) Turn all controls and the sensitivity knob to the OFF position or zero setting. Plug the leak detector into an approved source of voltage if not battery operated. Turn the switch ON, and allow the unit to warm up for approximately 5 minutes.

2) Check operation of the tester by positioning the probe in a reference source where refrigerant is known to be present in small amounts. Adjust the controls and sensitivity knob until detector reacts properly. Move probe away from refrigerant source and the reaction should stop. If it continues, adjust the sensitivity knob to a lower setting.

3) When tester reacts properly, leak test air conditioning system by moving probe under all components, fittings and connections. Keep the probe moving. DO NOT hold it in constant contact with refrigerant. When leaks are found, repair them as necessary. Keep in mind that there may be more than one leak.

DYE SOLUTION LEAK TESTING PROCEDURES

The following procedure is for introducing a dye solution, not dye-charged refrigerant, into the air conditioning system

1) Connect manifold gauge set to air conditioning system in a normal manner. Remove center hose from manifold gauge set, and replace it with a short piece (6" long) of 1/4" tubing using two 1/4" flare nuts. Connect a container of dye solution to the tubing.

2) Connect one end of the gauge set's center hose to the dye solution. Connect a container of refrigerant to the other end of the hose. Operate the engine at idle speed. Set the air conditioning system for maximum cooling. Slowly open the low-side hand valve to allow the dye solution to enter the system.

3) Charge the system to at least 50% capacity. Operate the system for 15 minutes, and then shut off both the air conditioning system and the engine. Check all connections for signs of the colored dye solution. Check the vehicle again 24 hours later. If leaks are found, repair as necessary.

See also:
• A/C COMPRESSOR SERVICING
• A/C COMPRESSOR REFRIGERANT OIL CHECKING