GM Blazer/Jimmy/Typhoon/Bravada 1983-1993 Repair Guide

Air Conditioning

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All 1995 trucks covered by this repair guide should be equipped with a new refrigerant (R-134a) to which the automotive industry is slowly changing over to prevent R-12 ozone damage. This new refrigerant is not available commercially in most areas and it is usually illegal to service a vehicle with this refrigerant. If you have a 1995 truck, the vehicle should be taken to a qualified technician for all A/C system service.

SAFETY PRECAUTIONS



Because of the inherent dangers involved with working on air conditioning systems and R-12 refrigerant, the following safety precautions must be strictly adhered to in order to service the system safely.

All 1995 trucks covered by this information are equipped with R-134a NOT R-12 refrigerant. These 2 refrigerants are NOT compatible. Using the incorrect refrigerant in an R-134a system will lead to compressor failure, refrigerant oil sludge and/or poor air conditioning system performance.

  1. Avoid contact with a charged refrigeration system, even when working on another part of the air conditioning system or vehicle. If a heavy tool comes into contact with a section of tubing or a heat exchanger, it can easily cause the relatively soft material to rupture.
  2.  
  3. When it is necessary to apply force to a fitting which contains refrigerant, as when checking that all system couplings are securely tightened, use a wrench on both parts of the fitting involved, if possible. This will avoid putting torque on refrigerant tubing. (It is advisable, when possible, to use tube or line wrenches when tightening these flare nut fittings.)
  4.  

R-12 refrigerant is a chlorofluorocarbon which, when released into the atmosphere, can contribute to the depletion of the ozone layer in the upper atmosphere. Ozone filters out harmful radiation from the sun.

  1. Do not attempt to discharge the system by merely loosening a fitting, or removing the service valve caps and cracking these valves. Precise control is possible only when using the service gauges and a proper A/C refrigerant recovery station. Wear protective gloves when connecting or disconnecting service gauge hoses.
  2.  

Be sure to consult the laws in your area before servicing the air conditioning system. In some states, it is illegal to perform repairs involving refrigerant unless the work is done by a certified technician.

  1. Discharge the system only in a well ventilated area, as high concentrations of the gas which might accidentally escape can exclude oxygen and act as an anesthetic. When leak testing or soldering, this is particularly important, as toxic gas is formed when R-12 contacts any flame.
  2.  
  3. Never start a system without first verifying that both service valves are properly installed, and that all fittings throughout the system are snugly connected.
  4.  
  5. Avoid applying heat to any refrigerant line or storage vessel. Charging may be aided by using water heated to less than 125°F (50°C) to warm the refrigerant container. Never allow a refrigerant storage container to sit out in the sun, or near any other source of heat, such as a radiator.
  6.  
  7. Always wear goggles to protect your eyes when working on a system. If refrigerant contacts the eyes, it is advisable in all cases to see a physician as soon as possible.
  8.  
  9. Frostbite from liquid refrigerant should be treated by first gradually warming the area with cool water, and then gently applying petroleum jelly. A physician should be consulted.
  10.  
  11. Always keep refrigerant drum fittings capped when not in use. If the container is equipped with a safety cap to protect the valve, make sure the cap is in place when the can is not being used. Avoid sudden shock to the drum, which might occur from dropping it, or from banging a heavy tool against it. Never carry a drum in the passenger compartment of a car.
  12.  
  13. Always completely discharge the system into a suitable recovery unit before painting the vehicle (if the paint is to be baked on), or before welding anywhere near refrigerant lines.
  14.  
  15. When servicing the system, minimize the time that any refrigerant line or fitting is open to the air in order to prevent moisture or dirt from entering the system. Contaminants such as moisture or dirt can damage internal system components. Always replace O-rings on lines or fittings which are disconnected. Prior to installation coat, but do not soak, replacement O-rings with suitable compressor oil.
  16.  

Most repair work on an air conditioning system should be left to a certified professional. DO NOT, under any circumstances, attempt to loosen or tighten any fittings or perform any work other than that outlined here.

GENERAL SERVICING PROCEDURES



See Figures 1 and 2

It is recommended, and possibly required by law, that a qualified technician perform the following services.

The most important aspect of air conditioning service is the maintenance of a pure and adequate charge of refrigerant in the system. A refrigeration system cannot function properly if a significant percentage of the charge is lost. Leaks are common because the severe vibration encountered underhood in a truck can easily cause cracking or loosening of the air conditioning fittings; allowing, the extreme operating pressures of the system to force refrigerant out.

The problem can be understood by considering what happens to the system as it is operated with a continuous leak. Because the expansion valve (tube or orifice on most late model vehicles) regulates the flow of refrigerant to the evaporator, the level of refrigerant there is fairly constant. The accumulator stores any excess of refrigerant, and so a loss will first appear there as a reduction in the level of liquid. As this level nears the bottom of the vessel, some refrigerant vapor bubbles will begin to appear in the stream of liquid supplied to the expansion valve. This vapor decreases the capacity of the expansion valve very little as the valve opens to compensate for its presence. As the quantity of liquid in the condenser decreases, the operating pressure will drop (there and throughout the high side of the system). As the R-12 continues to be expelled, the pressure available to force the liquid through the expansion valve will continue to decrease, and, eventually, the valve's orifice will prove to be too much of a restriction for adequate flow even with the needle fully withdrawn.



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Fig. Fig. 1: Air conditioning system schematic



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Fig. Fig. 2: Sectional view of a common A/C system orifice tube

At this point, low side pressure will start to drop, and a severe reduction in cooling capacity, marked by freeze-up of the evaporator coil, will result. Eventually, the operating pressure of the evaporator will be lower than the pressure of the atmosphere surrounding it, and air will be drawn into the system wherever there are leaks in the low side.

Because all atmospheric air contains at least some moisture, water will enter the system mixing with the R-12 and the oil. Trace amounts of moisture will cause sludging of the oil, and corrosion of the system. Saturation and clogging of the filter/drier, and freezing of the expansion valve orifice will eventually result. As air fills the system to a greater and greater extent, it will interfere more and more with the normal flows of refrigerant and heat.

From this description, it should be obvious that much of the repairman's time will be spent detecting leaks, repairing them, and then restoring the purity and quantity of the refrigerant charge. A list of general rules should be followed in addition to all safety precautions:

  1. Keep all tools as clean and dry as possible.
  2.  
  3. Thoroughly purge the service gauges and hoses of air and moisture before connecting them to the system. Keep them capped when not in use.
  4.  
  5. Thoroughly clean any refrigerant fitting before disconnecting it, in order to minimize the entrance of dirt into the system.
  6.  
  7. Plan any operation that requires opening the system beforehand, in order to minimize the length of time it will be exposed to open air. Cap or seal the open ends to minimize the entrance of foreign material.
  8.  
  9. When adding oil, pour it through an extremely clean and dry tube or funnel. Keep the oil capped whenever possible. Do not use oil that has not been kept tightly sealed.
  10.  
  11. Use only R-12 refrigerant. Purchase refrigerant intended for use only in automotive air conditioning systems. Avoid the use of R-12 that may be packaged for other purposes, such as cleaning, or powering a horn, as it is impure.
  12.  
  13. Completely evacuate any system that has been opened to replace a component, or that has leaked sufficiently to draw in moisture and air. This requires evacuating air and moisture with a good vacuum pump for at least one hour. If a system has been open for a considerable length of time it may be advisable to evacuate the system for up to 12 hours (overnight).
  14.  
  15. Use a wrench on both halves of a fitting that is to be disconnected, so as to avoid placing torque on any of the refrigerant lines.
  16.  
  17. When overhauling a compressor, pour some of the oil into a clean glass and inspect it. If there is evidence of dirt, metal particles, or both, flush all refrigerant components with clean refrigerant before evacuating and recharging the system. In addition, if metal particles are present, the compressor should be replaced.
  18.  
  19. Schrader valves may leak only when under full operating pressure. Therefore, if leakage is suspected but cannot be located, operate the system with a full charge of refrigerant and look for leaks from all Schrader valves. Replace any faulty valves.
  20.  

Additional Preventive Maintenance Checks
ANTIFREEZE

In order to prevent heater core freeze-up during A/C operation, it is necessary to maintain permanent type antifreeze protection of +15°F, or lower. A reading of -15°F is ideal since this protection also supplies sufficient corrosion inhibitors for the protection of the engine cooling system.

The same antifreeze should not be used longer than the manufacturer specifies.

RADIATOR CAP

For efficient operation of an air conditioned car's cooling system, the radiator cap should have a holding pressure which meets the manufacturer's specifications. A cap which fails to hold these pressures should be replaced.

CONDENSER

Any obstruction of or damage to the condenser configuration will restrict the air flow which is essential to its efficient operation. It is therefore a good rule to keep this unit clean and in proper physical shape.

CONDENSATION DRAIN TUBE

This single molded drain tube expels the condensation, which accumulates on the bottom of the evaporator housing, into the engine compartment. If this tube is obstructed, the air conditioning performance can be restricted and condensation buildup can spill over onto the vehicle's floor.

AIR CONDITIONING TOOLS



See Figures 3 and 4

Test Gauges

Most of the service work performed in air conditioning requires the use of a set of two gauges, one for the high (head) pressure side of the system, the other for the low (suction) side.



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Fig. Fig. 3: Manifold gauges connected for evacuation and charging



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Fig. Fig. 4: Accumulator with Schrader valve

The low side gauge records both pressure and vacuum. Vacuum readings are calibrated from 0 to 30 inches and the pressure graduations read from 0 to no less than 60 psi (414kPa). The high side gauge measures pressure from 0 to at least 600 psi (4140kPa).

Both gauges are threaded into a manifold that contains two hand shut-off valves. Proper manipulation of these valves and the use of the attached test hoses allow the user to perform the following services:

  1. Test high and low side pressures.
  2.  
  3. Remove air, moisture, and contaminated refrigerant.
  4.  
  5. Charge the system (with refrigerant).
  6.  

The manifold valves are designed so they have no direct effect on gauge readings, but serve only to provide for the flow or cut-off of refrigerant through the manifold. During all testing and hook-up operations, the valves are kept in a closed position to avoid disturbing the refrigeration system. The valves are opened only to purge the system of refrigerant or to charge it.

When purging the system, the center hose is attached to a suitable recovery station at the lower end, and both valves are cracked open slightly. This allows refrigerant pressure to force the entire contents of the system out through the center hose and into the recovery station. During charging, the valve on the high side of the manifold is closed, and the valve on the low side is cracked open. Under these conditions, the low pressure in the evaporator will draw refrigerant from the relatively warm refrigerant storage container into the system.

Service Valves

For the user to diagnose an air conditioning system he or she must gain "entrance" to the system in order to observe the pressures; the type of terminal for this purpose is the familiar Schrader valve.

The Schrader valve is similar to a tire valve stem and the process of connecting the test hoses is the same as threading a hand pump outlet hose to a bicycle tire. As the test hose is threaded to the service port the valve core is depressed, allowing the refrigerant to enter the test hose outlet. Removal of the test hose automatically closes the system.

Extreme caution must be observed when removing test hoses from the Schrader valves as some refrigerant will normally escape.

Using The Manifold Gauges

Refer to the following as a step-by-step guide to correct gauge usage.

  1. WEAR GOGGLES OR FACE SHIELD DURING ALL TESTING OPERATIONS. BACKSEAT ANY HAND SHUT-OFF TYPE SERVICE VALVES.
  2.  
  3. Remove caps from high and low side service ports. Make sure both gauge valves are closed.
  4.  
  5. Connect low side test hose to the service valve that leads to the evaporator (located between the evaporator outlet and the compressor). On some vehicles the low side port may be located on or near the accumulator.
  6.  
  7. Attach high side test hose to the service valve that leads to the condenser.
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  9. Mid-position the hand shutoff type service valves.
  10.  
  11. Start engine and allow for warm-up. All testing and charging of the system should be done after the engine and the system have both reached normal operation temperatures (unless the recovery/charging station's manufacturer instructs otherwise).
  12.  
  13. Adjust air conditioner controls to maximum cold.
  14.  
  15. Observe gauge readings. When the gauges are not being used it is a good idea to:
    1. Keep both hand valves in the closed position.
    2.  
    3. Attach both ends of the high and low service hoses to the manifold, if extra outlets are present on the manifold, or plug them if not. Also, keep the center charging hose attached to an empty refrigerant can. This extra precaution will reduce the possibility of moisture entering the gauges. If air and moisture have gotten into the gauges, purge the hoses by supplying refrigerant under pressure to the center hose with both gauge valves open and all openings unplugged.
    4.  

  16.  

SYSTEM INSPECTION



The Cycling Clutch Office Tube (CCOT) A/C system does not use a sight glass.

The easiest and often most important check for the air conditioning system consists of a visual inspection of the system components. Visually inspect the air conditioning system for refrigerant leaks, damaged compressor clutch, compressor drive belt tension and condition, plugged evaporator drain tube, blocked condenser fins, disconnected or broken wires, blown fuses, corroded connections and poor insulation.

R-12 refrigerant is a chlorofluorocarbon which, when released into the atmosphere, can contribute to the depletion of the ozone layer in the upper atmosphere. Ozone filters out harmful radiation from the sun.

A refrigerant leak will usually appear as an oily residue at the leakage point in the system. The oily residue soon picks up dust or dirt particles from the surrounding air and appears greasy. Through time, this will build up and appear to be a heavy, dirt impregnated grease. Most leaks are caused by damaged or missing O-ring seals at the component connections, damaged charging valve cores or missing service gauge port caps.

For a thorough visual and operational inspection, check the following:

  1. Check the surface of the radiator and condenser for dirt, leaves or other material which might block air flow.
  2.  
  3. Check for kinks in hoses and lines. Check the system for leaks.
  4.  
  5. Make sure the drive belt is under the proper tension. When the air conditioning is operating, make sure the drive belt is free of noise or slippage.
  6.  
  7. Make sure the blower motor operates at all appropriate positions, then check for distribution of the air from all outlets with the blower on HIGH.
  8.  

Keep in mind that under conditions of high humidity, air discharged from the A/C vents may not feel as cold as expected, even if the system is working properly. This is because the vaporized moisture in humid air retains heat more effectively than does dry air, making the humid air more difficult to cool.

  1. Make sure the air passage selection lever is operating correctly. Start the engine and warm it to normal operating temperature, then make sure the hot/cold selection lever is operating correctly.
  2.  

REFRIGERANT LEVEL CHECKS




CAUTION
Do not attempt to charge or discharge the refrigerant system unless you have access to a recovery station and are thoroughly familiar with the system's operation and the hazards involved. The compressed refrigerant used in the air conditioning system expands and evaporates (boils) into the atmosphere at a temperature of -21.7°F (-29.8°C) or less. This will freeze any surface that it comes in contact with, including your eyes. In addition, the refrigerant decomposes into a poisonous gas in the presence of flame.

The factory installed A/C systems on almost all vehicles covered by this information are a Cycling Clutch Orifice Tube (CCOT) system which does not include a sight glass. The CCOT refrigeration system is designed to cycle the compressor on and off to maintain desired cooling and to prevent evaporator freeze. A few of the later model vehicles equipped with the 2.5L (VIN E) engine may be equipped with a Variable Displacement Orifice Tube (VDOT) system. The VDOT system employs a constant run V-5 compressor which is a variable displacement unit capable of matching the air conditioning demand for all normal operating conditions without cycling. Both systems are serviced similarly, but most parts are not interchangeable.

If your truck is equipped with an aftermarket air conditioner, the following system checks may not apply. Contact the A/C system manufacturer for instructions on system checks.

The air conditioning system on these vehicles has no sight glass.

  1. Run the engine until it reaches normal operating temperature.
  2.  
  3. Open the hood and all doors.
  4.  
  5. Turn the air conditioning ON, move the temperature selector to the first detent to the right of COLD (outside air) and then turn the blower on HI.
  6.  
  7. Idle the engine at 1,000 rpm.
  8.  
  9. Feel the temperature of the evaporator inlet and the accumulator outlet with the compressor clutch engaged.
  10.  
  11. Both lines should be cold. If the inlet pipe is colder than the outlet pipe, the system is low on charge. Do not attempt to charge the system yourself unless you have access to the proper equipment.
  12.  

DISCHARGING THE SYSTEM



R-12 refrigerant is a chlorofluorocarbon which, when released into the atmosphere, can contribute to the depletion of the ozone layer in the upper atmosphere. Ozone filters out harmful radiation from the sun.

Consult the laws in your area before servicing the air conditioning system. In some states it is illegal to perform repairs involving refrigerant unless the work is done by a certified technician.

The use of refrigerant recovery systems and recycling stations makes possible the recovery and reuse of refrigerant after contaminants and moisture have been removed. If a recovery system or recycling station is available, the following general procedures should be observed, in addition to the operating instructions provided by the equipment manufacturer.

  1. Check the system for pressure using the manifold gauge set. Take note, if a recovery system is used to draw refrigerant from a system that is already ruptured and open to the atmosphere, only air may be pulled into the tank.
  2.  
  3. Connect the refrigerant recycling station hose(s) to the vehicle air conditioning service ports and the recovery station inlet fitting.
  4.  

Hoses should have shut off devices or check valves within 12 in. (305mm) of the hose end to minimize the introduction of air into the recycling station and to minimize the amount of refrigerant released when a hose is disconnected.

  1. Turn the power to the recycling station ON to start the recovery process. Allow the recycling station to pump the refrigerant from the system until the station pressure goes into a vacuum. On some stations the pump will be shut off automatically by a low pressure switch in the electrical system. On other units it may be necessary to manually turn off the pump.
  2.  
  3. Once the recycling station has evacuated the vehicle air conditioning system, close the station inlet valve, if equipped. Then switch OFF the electrical power.
  4.  
  5. Allow the vehicle air conditioning system to remain closed for about 2 minutes. Observe the system vacuum level as shown on the gauge. If the pressure does not rise, disconnect the recycling station hose(s).
  6.  
  7. If the system pressure rises, repeat Steps 3, 4 and 5 until the vacuum level remains stable for 2 minutes.
  8.  
  9. If A/C oil is expelled during the discharge procedure, before discarding the oil, measure the amount discharged in order to determine the proper quantity which must be added to the system during charging.
  10.  

EVACUATING/CHARGING THE SYSTEM



All 1995 trucks covered by this information are equipped with R-134a NOT R-12 refrigerant. These 2 refrigerants are NOT compatible. Using the incorrect refrigerant in an R-134a system will lead to compressor failure, refrigerant oil sludge and/or poor air conditioning system performance.

Evacuating and charging the air conditioning system is a combined procedure in which the lines are purged, then refrigerant is added to the system in proper quantity. Charging is always conducted through the low pressure fitting. NEVER attempt to charge the air conditioning through the high pressure side of the system.

Once again, evacuation and charging should not be attempted unless the proper equipment, such as a charging station and a vacuum pump, is available in order to properly service the system. If these tools are available, the following general procedures should be observed, in addition to the operating instructions provided by the equipment manufacturer.

  1. The proper amount of fresh compressor oil must be added to the system after discharging, but BEFORE evacuation and charging. The total amount of oil which was lost from the system during discharge and from any repaired or replaced components must be added to the system. This can be accomplished by disconnecting the refrigeration suction hose at the accumulator outlet pipe connection and by pouring the fresh oil into the hose or pipe and then reconnecting the fitting.
  2.  
  3. Properly connect a manifold gauge set to the vehicle, then connect the manifold to a vacuum pump.
  4.  
  5. Turn the vacuum pump ON and slowly open the high and low side valves to the pump. Allow the system to evacuate for 20-30 minutes, then note the gauge reading. If the system is unable to reach 28-29 in. of vacuum, the system and vacuum pump must be checked for leaks and repaired before proceeding further.
  6.  
  7. After the system has been evacuated for a minimum of 20 minutes, close the gauge high and low side valves, then shut the pump OFF.
  8.  
  9. Watch the low side gauge for vacuum loss. If vacuum loss is in excess of 1 in. Hg (3.38 kPa), then leak test the system, repair the leaks and return to Step 1. Before leak testing, remember to disconnect the gauge high side connector from the service port.
  10.  
  11. If after 1-3 minutes, the loss is less than 1 in. Hg (3.38 kPa), then proceed with the system charging.
  12.  
  13. Disconnect the gauge high side connection from the service port and the gauge manifold from the vacuum pump.
  14.  
  15. Engage the center manifold connection to an R-12 source. If you are using a refrigerant drum instead of a charging station, place the drum on a scale to determine the amount of refrigerant being used.
  16.  
  17. Open the source and low side gauge valve, then monitor the weight of the drum or the rate at which the charging system is introducing R-12 into the system.
  18.  
  19. When 1 lb. of R-12 has been added to the system, start the engine and turn the air conditioning system ON. Set the temperature lever to full cold, the blower speed on high and the selector lever to the upper outlets. Under this condition, slowly draw in the remainder of the R-12 charge. The total charge will vary depending on the model and system, but may range anywhere between 2-4 lbs.
  20.  
  21. When the system is charged, turn the source valve OFF and continue to run the engine for 30 seconds in order to clear the gauges and lines.
  22.  
  23. With the engine still running, carefully remove the gauge low side hose from the suction pipe service fitting. Unscrew the connection rapidly to avoid excess refrigerant loss.
  24.  


CAUTION
If the hoses of the manifold gauge set may be disconnected from the gauge, NEVER remove a hose from the gauge while the other end of the hose is still connected to an air conditioning system service fitting. Because the service fitting check valve is depressed by the hose connection, this would cause a complete and uncontrolled discharge of the system. Serious personal injury could be caused by the escaping refrigerant.

  1. Install the protective service fitting caps and hand-tighten.
  2.  
  3. Turn the engine and air conditioning OFF .
  4.  
  5. If an electronic or open flame leak tester is available, test the system for leaks.
  6.  
  7. If there are no leaks, perform the refrigerant level test to verify proper system charging.
  8.  

LEAK TESTING THE SYSTEM



Whenever a refrigerant leak is suspected, begin by checking for leaks at the fittings and valves. There are several methods of detecting leaks in an air conditioning system; among them, the two most popular are (1) halide leak-detection or the "open flame method," and (2) electronic leak-detection. Use of an electronic leak detector, if available is preferable for ease and safety of operation.

The halide leak detector is a torch like device which produces a yellow-green color when refrigerant is introduced into the flame at the burner. A purple or violet color indicates the presence of large amounts of refrigerant at the burner.

An electronic leak detector is a small portable electronic device with an extended probe. With the unit activated the probe is passed along those components of the system which contain refrigerant. If a leak is detected, the unit will sound an alarm signal or activate a display signal depending on the manufacturer's design. Follow the manufacturer's instructions carefully. Move the detector probe at approximately 1 in. (25mm) per second in the suspected leak area. When escaping refrigerant gas is located, the ticking/beeping signal from the detector will increase in ticks/beeps per second. If the gas is relatively concentrated, the signal will be increasingly shrill.


CAUTION
Care should be taken to operate either type of detector in well ventilated areas, so as to reduce the chance of personal injury, which may result from coming in contact with poisonous gases produced when R-12 is exposed to flame or electric spark.

If a tester is not available, perform a visual inspection and apply a soap solution to the questionable fitting or area. Bubbles will form to indicate a leak. Make sure to rinse the solution from the fitting before attempting repairs.

 
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