Thanks for reponse. Sorry, I should have been more specific. The green light is on the adapter. It is supposed to come on after holding for 5 sec on a system that has stabuilized flow (about 5 minutes running puymp). The green light on the adapter lights up, but it begins to flash (i.e. does not stay lit up). This is what happened to me originally one month ago so I replaced tri-sensor and also replaced adapter that came with it. Recently the adapter would not stay green after calibration, it flashed on and off. So, after inspecting sensors (OK), I replaced the adapter with the old one I had swapped out and it began to work again. Although it's a bit of shotgunning the trouble, it seems the adapter went bad. Has anyone had expeience with a bad adapter. What does the flashing mean (bad adapter or bad flow sensor).