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Refrigerant Leak Checks

Refrigerant Leak Checks. R-134a Molecule. Both R-12 and R-134a are heavier than air; the gas escaping through a leak will normally fall downward. The R-134a molecule is smaller than R-12 so a similar leak will have a greater leak rate with R-134a. Probable Leak Locations.

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Refrigerant Leak Checks

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  1. Refrigerant Leak Checks

  2. R-134a Molecule Both R-12 and R-134a are heavier than air; the gas escaping through a leak will normally fall downward. The R-134a molecule is smaller than R-12 so a similar leak will have a greater leak rate with R-134a.

  3. Probable Leak Locations Most leaks will occur at line fittings. Also, suspect the compressor shaft seal, service fittings, switches and sensors, and check the evaporator drain. Look for any rub-throughs; these are where a metal line or rubber hose rubs against metal.

  4. Spring Lock Connectors Check any snap lock connectors (white circle). These two have retainers to help stabilize the two parts. The oily dust (yellow circle) is an indication of a possible refrigerant leak.

  5. Leak Checking Aids • When searching for a leak, make sure: • The system has at least 50 psi • The area is free from wind or drafts • The engine is shut off • When checking a particular place, leave the leak detector search probe stationary for 5 seconds • If a leak is found, move the leak detector search probe away and then back in to verify the leak • Follow the SAE procedure SAE #J1628

  6. Electronic Leak Detectors Two different electronic leak detectors. When the probe is brought close to a refrigerant leak the detector will indicate the leak by a flashing light or electronic sound. These detectors require periodic maintenance like replacement of the filter in the probe.

  7. Maintenance Sensing Tip Battery powered leak detectors must have a properly charged battery. This electronic leak detector uses a replaceable sensing tip. Some detectors have a replaceable filter inside of the tip. The tip/filter must be clean for the detector to work properly.

  8. Search Procedure The tip of the probe should be kept about 1/4 in. away from the tubing, hose, or fitting. It should be moved all the way around each possible leak location.

  9. Search Rate Keep the search probe about 1/4 in. away from the hose, and move it along the hose at a rate of about 2 in per second. Pay close attention to hose connections and any rubbed areas or bulges in a hose.

  10. Internal Pressure Internal pressure pushes refrigerant through the leak. The greater the pressure, the faster the leak rate, and the easier it will be to find. Run the system, and check the high side right after you shut it off. Check the low side after a few minutes and the pressure rises. An evaporator leak rate will increase if you run the heater, and then shut the system off and allow the evaporator to heat soak for a few minutes. Check for leaks at the evaporator drain.

  11. Fluorescent Dye This kit contains an injector to put the dye into a system, adapter to connect the injector to the system, a UV lamp to make the dye fluoresce, and a goggles to protect your eyes and help the leak show up. The dye (about 1/4 oz) is added to the system, the system is operated, and then the UV lamp is used to find where the dye and refrigerant leak out.

  12. Dye Dye is available in various containers. Next to the left is a pressurized container of refrigerant and dye. The oil that carries the dye is water-soluble so it can usually be removed using a water rinse.

  13. A Leak Under the UV light, the dye fluoresces and glows.The yellow-green stain indicates a leaky hose connection. This hose needs to be replaced or a new end fitting needs to be put on the hose.

  14. Other Methods, Soap A soap mixture can be applied to a suspected leak location. The bubbles from escaping refrigerant gas show the exact location of the leak.

  15. Other Methods, Ultrasonic The upper portion of this tester can receive the sound of a refrigerant leak. This sound is often in the ultrasonic frequency that we normally can not hear. The tester converts the sound frequency so we can hear it using a headset, and it also displays the sound/leak rate.

  16. Tip: Compressor Shaft Seal An oil thrown off the compressor clutch is an indication of a shaft seal leak. Place a business card between the clutch plate and rotor, and cycle the clutch. Oil on the card will confirm the leak; the compressor shaft seal needs to be replaced.

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