[Andrew B]

It could be the gas bench is working but full of dust or a communication error with the main board. Amps clamps were always "victims" of abuse by garage tech's "snapping" their jaws together, the sensor in them is a hall effect <blob> stuck on an aluminium plate, careful dismantling work and examination of the cord may reveal a simple fault. I used to replace the tant beads on sight with aluminium electrolytics, there's plenty of space on the boards. Good luck.