I would like to share typical sources of leaks on Suburbans and Tahoe’s. Here are a couple. Feel free to add where you have found leaks.

1. The fitting where the hi pressure AC line bolts to the evaporator right at the firewall.

2. Anywhere along the high pressure line to the rear evaporator. Look underneath the vehicle. The lines are mounted on the frame along the passenger side.

3. Adjacent to the passenger side rear wheel. You have to crawl under the truck to see the area between the tire and frame. The lines take several bends and tend to corrode right underneath the straps that hold the lines to the frame.

There should be dye from the factory in the system. Use a blacklight to look for leaks. Here is the tell tale factory dye showing the leak at the front evaporator fitting.



On the right you can see the dye where the refrigerant leaked out. Visable with a black light.

 

Picture in initial post shows much-improved connector design than the earlier models.

Service valves - and especially service valve caps - are also common sources of refrigerant leakage. The caps are the real seal, and the rubber O-Ring in them can crack and leak. See photo of bad R-12 cap below.