HVAC Systems - General Servicing: Diagnosis Chevrolet Silverado 2500

LEAK TESTING

PREPARATION FOR LEAK TESTING

Connect manifold gauge set to A/C system. Ensure low-side and high-side gauge set valves are closed. Check system pressure. Pressure 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 dauber that comes with commercial soap solution, apply solution to all joints, connections, fittings or controls where a leak might be suspected. If high-suds household solutions are used, apply with a small brush. Wherever bubbles form, leaks are present and must be repaired. Check 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 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 around explosive gases. Always follow manufacturers instructions for 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 to ON position and allow unit to warm up for about 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 reaction should stop. If reaction continues, adjust sensitivity knob to a lower setting.
3. When tester reacts properly, leak test A/C system by moving probe under all components, fittings and connections. Keep 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 as necessary. Keep in mind, 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 A/C 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 tubing.
2. Connect one end of gauge set center hose to dye solution container. Connect a container of refrigerant to other end of hose. Operate engine at idle. Set A/C system for maximum cooling. Slowly open low-side hand valve to allow dye solution to enter system.
3. Charge system to at least 50 percent capacity. Operate system for 15 minutes and then shut off both A/C system and engine. Check all connections for signs of colored dye solution. Check vehicle again 24 hours later. If leaks are found, repair as necessary.

FLUORESCENT DYE LEAK TESTING PROCEDURES

Note. Fluorescent leak detection method is intended to be used in conjunction with an electronic leak detection method, to pinpoint smaller leaks. Fluorescent dye takes time to work. Depending on leak rate, dye could take up to 7 days to become visible after installation into A/C system.

Note. After refrigerant dye is installed into A/C system, complete refrigerant leak detection notice sticker (supplied with dye package) and place next to underhood charge label.

1. Start engine and allow to idle. Turn A/C system on and controls to maximum cold position. Ensure compressor clutch is engaged. If compressor clutch stays engaged at idle, low side refrigerant pressure is sufficient to check for a leak. If necessary, charge A/C system so compressor clutch will operate.
2. If A/C system is charged, install fluorescent leak detection dye using R-134a A/C tracer dye injector. Follow dye injector manufacturer instructions. If A/C system is discharged, add dye to replacement component with specified amount of refrigerant oil.
3. After installing dye, clean low side fitting to remove any residue, using fluorescent dye cleaner or general purpose oil solvent. Observe and record ambient air temperature and humidity. Place thermometer in center A/C outlet duct.
4. Start engine. Turn A/C system on and controls to maximum cold position. Increase engine speed to 1500 RPM. After about 5 minutes, record outlet temperature displayed on center A/C outlet duct thermometer. If outlet temperature is at least 20°F (11°C) colder than ambient temperature, A/C system is operating properly.
5. Turn engine off. Check for refrigerant leaks using an electronic leak detector. See «ELECTRONIC LEAK TESTING PROCEDURE»(ref-156625-S16407012042003072300000) . Perform repairs as necessary. If no leaks are found, go to next step.
6. Using Leak Detection Lamp Kit (J42220) UV lamp and Yellow glasses, slowly pan A/C system with UV lamp directed toward all possible leak areas. When a leak is found, fluorescent dye, when viewed through Yellow glasses and highlighted with UV lamp, will glow Light Green or Yellow/Green.
7. Leak detection dye mixes with refrigerant PAG oil. Therefore, extremely small leaks may be pressure, temperature or vibration sensitive and may not be active during a 5 minute test. It may be necessary to request vehicle be returned for further testing in 3 to 5 days. Because detection dye and PAG oil are water soluble, vehicles driven in rain, through sprinkler puddles, etc., may experience leak detection problems.
8. Perform repairs as necessary. Clean A/C system components, especially repaired area, using a Leak Dye Cleaner (J43872) or water until dye can no longer be detected. Start engine and allow to idle. Operate A/C system at maximum cold settings for 5 minutes and recheck for leaks.