Hf coupler fault on both sys in C-130 Technical Posted September 17 Don't know why the #1 system pressure would affect #2. The worst thing the USAF did was put two 99.9% error free systems on the same bird. Woud have been so much better without the second system. The RF interlock system is ridiculously designed. I don't see that causing your problem. Wish I could be of more help.