Finding refrigerant leaks is a major aspect of A/C service. It makes no sense to recharge a leaky system with refrigerant if it will soon leak back out. Ultraviolet dyes can make even the smallest leaks clearly visible. But not all OEMs approve of their use. The domestic OEMs (Ford, GM and Chrysler) all use and approve the use of dyes. The only import vehicle manufacturer who has publicly endorsed the use of dye is Nissan (since 1999).

Honda, Mazda, Toyota, Hyundai and Mercedes-Benz currently do not use or endorse the use of dye to find leaks. One reason they may be leery of dye is because using too much may dilute the compressor lubricant and increase the risk of compressor noise and failure. The standard recommended dose is only one-quarter ounce. A second dose won't usually result in any problems, but multiple doses over a period of time can overload the system with dye and cause trouble.

Evaporator Issues
Evaporator leaks can be expensive to fix because the labor alone may be eight to 12 hours or more depending on the application. For customers who can't afford such a repair, a sealer may offer a less expensive fix - though no promises should be made as to how long the leak repair will hold or if it will seal the leak at all.

When evaporator leaks are caused by external corrosion, the culprit is often an accumulation of leaves and debris in the evaporator case. The debris traps moisture and promotes metal...