- Use only dyes that meet SAE J2297.
- Before injecting dye, look underneath the hood for a sticker indicating whether dye has already been installed. Alternately, remove the low-side service port cap and depress the valve stem for an instant to determine if dye is in the system. If dye is present, proceed to check for leaks.
- Add dye according to the manufacturer’s instructions, provided that no dye was added previously to the system.
- Place the identification label supplied by the dye manufacturer in a prominent place in the engine compartment (adjacent to the A/C charge label if possible).
- Verify that the A/C system has a sufficient refrigerant charge as per factory specifications; then operate the system for a minimum of 15 minutes to circulate the dye.
- Inspect the entire A/C system with a UV lamp with the engine off.
- Trace the entire refrigerant system concentrating on leak-prone locations, such as hose-to-line couplings, service ports and connections. Check for evaporator leaks by illuminating the condensate drain hole. Only large leaks may be detected at this stage, due to the limited length of time the dye has been allowed to accumulate at any leak location. If a leak cannot be found, ask the customer to return in a week or more, after operating the A/C system as much as possible. This extended operating time should cause sufficient dye to collect at the point of leakage, enabling detection.
- Continue to check the rest of the system even if a leak is found.
- Verify any small leak by using an electronic leak detector as per SAE Standard J1628 to determine whether the leak is of a repairable size as defined by the vehicle or motor vehicle air conditioning system manufacturer. Some compressor shaft seal lubricant leakage may be normal for the system in question.
- Remove any fluorescent residue using a cleaner approved by the vehicle or motor vehicle air conditioning system manufacturer after the leak is repaired. Although the use of fluorescent dyes is widespread in the A/C service industry, some manufacturers may prohibit using dyes, and others only permit specific dyes to be used. Always follow the manufacturer’s recommendations.
When using UV detectors, use care as ultraviolet light exposure can be hazardous to skin and eyes. To minimize UV exposure, wear UV-blocking eyewear, direct the light source away from your body and protect bare skin. Once again, the use of dyes must be acceptable by the A/C system and/or vehicle manufacturer, or meet the requirements of SAE J2297.
Stay tuned for more details about leak detection: It’s likely that a new refrigerant, HFO-1234yf, will replace R-134a. This will require some changes to both standards and leak detection equipment, so you’ll want to check back for the latest developments.
Cappert discusses questions about leak detection products