As with most growers, ive experienced problems with timers failing to switch off.The cause of that annoying little problem is the microswitch sticking,especially on the 18/6 cycle. Well,I idecided to try to fix the problem once and for all. What I did was drill a hole about a millimetre wide and put 3in 1 oil inside. I dont have that problem of sticking anymore. Be careful not to over oil it as it may screw it up. Hope that helps.