I am sorry but all that back flushing
doesn't work. It's a good practice for preventive maintenance
but we're talking about A/C line here and every time I've seen this problem, dis-assembly was needed.
I would replace the hose, but beating it on the ground much like a whip to get all the crud out works for some. Next is the condenser of the A/C itself. The only thing that works here is flushing with muriatic acid diluted with water. You need to recirculate that much like when cleaning
. The best technique is using the smallest Rule
submersible bilge pump
or a submersible livewell pump in a bucket with the acid-water mix.
I am currently renovating the forward thru-hull on Jedi. It supplies water to the A/C and a deck
wash pump. I made a PVC manifold with 4 valves/connections: sea-strainer, deck
wash pump, A/C pump and the 4th to be connected to the boat's pressure fresh water supply. This makes flushing the A/C circuit and deck wash very easy and the sea-strainer/thru-hull can be back-flushed. It also allows priming the circuits and even fresh water deck wash. It cost less than $20.