As I stated before, AC leaks are probably the number-one cause of poor AC system performance. Finding those leaks can be tricky, but there are tools out there to help you with that. There are two main tools used to find AC leaks. The first is a fluorescent dye you put into the system. When the refrigerant and the dye leak out, you can find the source with an ultraviolet light.
The second type is called a sniffer. This tool is placed near the suspected source of the leak. When it detects a refrigerant leak, it emits a beep or warning to the user. The faster the beep, the larger the leak.
Refrigerant dye is the most popular way to find AC leaks. It's cheap and definitive. A sniffer can be used in situations where you're not able to put your eyes on the potential source of the leak. Say you have a leaking evaporator located deep inside the dashboard; you can use the sniffer at the vent outlets to see if it detects a leak.
You can also use dye to find these leaks, but it's a little more difficult. If you suspect an evaporator leak and you want to check for it with dye, check the AC drain tube located under the vehicle. This is the tube that allows the condensation from the evaporator to leak out. When dye is placed in the system, it sometimes comes out with this condensation.
One last method to find leaks I almost forgot about, is with soapy water. You can also spray the suspected area with a soap and water solution, then observe the area for bubbles. If there’s a leak, you’ll see bubbles accumulate in the effected area. It may seem crude but it’s very effective for the exposed parts of the AC system. Here is a video showing the AC dye and sniffer methods.