Solenoid is made by wired copper, and the quality of copper wire is the key factor of transformer lifetime. The aluminum wire covered by copper with the same length is only one fourth the price of pure copper wire. Due to the cost pressure, transformer manufacturers would use aluminum wire covered by copper. This would lead to bread down failure when temperature raises, which further results in failure of light source and the whole LED Lights. How to tell apart pure copper wire and aluminum wire covered by copper? Simple light up the wire with a lighter, and the one burns quickly must be aluminum wire inside. It can also be tested by measuring coil resistance.