A common way to find the source of an air conditioning refrigerant leak is to inject fluorescent dye into the system. Once dye is circulating in the system, if there is a leak the dye will also leak out, and you can find where it’s leaking by shining a blacklight around various system components.
After recharging the system with the correct amount of refrigerant you connect a special tool onto one of the fittings and inject it in. I was doing this on a newer Honda Pilot, which uses the new refrigerant, R-1234yf, compared to the R-134a we’ve used for several years, and we have a different tool for dye injection on these new models. As I tried to connect it to the fitting, the pressure caused dye to spray all over the side of the engine, and it ran down onto the pulleys and got slung everywhere. It looks like an alien got caught in the accessory belt and died, getting its fluorescent blood everywhere.
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