Having had several of the above lights , I finally purchased 2 x 50W lights without PIR sensors and wired them through a separate sensor, and have had no trouble. I have 4 other lights and I have had to replace the chip on 2 of the and 3 PIR sensors. As they fail I'm nor going to mess about changing the integral PIR's, I'm going to spend a few more quid on a decent quality sensor. If the lamp fails it is easy to connect a power lead directly to the lamp and see it lights up. If it does its the sensor, if it doesn't it either the chip or the drive. To test the chip, buy a spare driver, access the chip connect the driver to the mains supply and using the output leads as probes, touch the respective chip connections with the lead from the driver module. It lis low voltage so there is little risk of a shock. It the chip doesn't light up, that's the problem, if it does, its the driver. I have taken the step of keeping a spare driver and spare chips, they are fairly cheap and enable fairly quick repairs. These lights are fairly basic, a casing, a driver, a chip and a sensor. A separate good quality sensor seems to solve the niggling problem of premature failure.