This problem could be a number of issues. It could be the switch assembly, wiring within the hose, the powerhead, a faulty connection with the extension wands, or an issue with your high voltage wiring. If you have inlet valves wired with high voltage receptacles and your Beam 1393 power head has a two prong cord, you could plug it in directly to the wall to elminate the power head as the issue. The only way to test if it's the wiring within the hose, is to have a special tool to measure continuity. If there isn't any intermittent power through the hose to the powerhead, it's usually not an issue with the extension wands. More often than not, the issue is with your switch assembly and is a simple fix. We have replacement switch assemblies, Switch Assembly for Gas Pump and Pistol Grip Style Hoses (Part #352GS and #352S) for hoses marked on the wall end cuff with the letter P within a small circle.