Keeps cutting out?

My drier cuts out after a couple of mins, thermostats ok heater works no fluff, condenser clear, water empty, the red wire on the relay that is used for self latching looses volts and the relay drops out. It will reset and immediately and run again by pressing the start switch. I thought the conntacts on the relay were at fault at first and cleaned those. I can not fathom where the feed comes from for the relay once it is latched and the machine is running. Any ideas please?