The device failed while sanding the baby bed. I used it for more than 7 hours straight on a hot and sunny day. I have owned and used other grinders and have never had this problem. They come with a lifetime guarantee which I voided for opening them. I thought it was the switch but it was perfect and I reinstalled it. I then removed the sealant from around the circuit and noticed that the MOSFET pin was melted and disconnected at the left connector. I don't know if an unlit center contact was used, I can find the device schematic. I could just plug it straight into the brushes as there is an on/off switch. This is my last tool, I have a rigid vacuum cleaner but that's about it. My next one will be light or dark blue. The lime green instrument has exactly the same details.