HVAC System - General Servicing: Diagnosis Chevrolet Metro I

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 the 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.

Breeze, Cirrus, Concorde, Intrepid, LHS, Stratus & 300M (Scan Tool Method)

1. Attach Diagnostic Readout Box (DRB) to Data Link Connector (DLC). Set DRB (scan tool) to PARTIAL CHARGE TEST. Attach clamp-on Thermocouple (80PK-1A) to liquid line, as close to condenser outlet as possible.
2. Set parking brake, and place transaxle in Park position. Start engine and allow to idle. Set A/C controls to outside air, panel mode, full cool, and high blower speed. Turn A/C on, and open vehicle windows. Operate A/C system for a few minutes to allow system to stabilize.
3. Place cardboard over front grille area, to block airflow through part of condenser, to set A/C system pressure to 260 psi (18.3 kg/cm 2 ). This will stop cooling fans from alternating speeds and maintain constant pressure.
4. Scan tool will automatically calculate system charge. Depending on system charge condition, corrections are made 2 ounces at a time. Each time a correction is made, recheck readings to ensure proper charge. For system refrigerant capacity, see REFRIGERANT OIL & REFRIGERANT SPECIFICATIONS article.

PREPARATION FOR LEAK TESTING

Connect manifold gauge set to air conditioning system. Ensure low-side and high-side gauge set valves are closed. Check system pressure. It should be at least 50 psi (3.5 kg/cm 2 ). If system is empty, evacuate A/C system and apply 28 in. Hg of vacuum. If system holds vacuum for 15 minutes there most likely are no leaks present. If low, add just enough refrigerant (about 10 ounces) 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.

Start engine and allow to idle. Operate A/C system for about 5 minutes. Set A/C controls to outside air, and high blower speed. Turn A/C on, and open vehicle windows. Turn engine off and wait 2-7 minutes. Refrigerant is 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 tester 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 detector sensitivity knob to OFF position or zero setting. Connect leak detector to an approved source of power. Turn switch ON, and allow unit to warm up for approximately 5 minutes.
2. Check operation of tester by positioning probe in a reference source where refrigerant is known to be present in small amounts. Adjust 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. To check evaporator insert probe into drain tube opening or a heater duct. DO NOT allow probe to contact refrigerant or refrigerant oil. 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 A/C 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 gauge set center hose to dye solution container. Connect a container of refrigerant to the other end of the hose. Operate 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 system to at least 50 percent capacity. Operate 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.