Too many imponderables here....'you worked on it'....what's that supposed to mean? And why would turning it on and off make it work properly? If you know anything about Electronics you might be able to fix it! When a PIR stays on/off it is usually a sign of component failure. Suspect the Relay first,then check the load (current) resistor,which in your case,could have gone 'high'.There are other components to check too,but you will be expected to have a good knowledge in this field - otherwise give it to someone who has.
I find that if you lower the 'default' voltage of the bulb,the PIR will not give too many problems,as the manufacturers tend to work on the 'margins' when it comes to 'load' components - although quite safe! Also,you may well find that it could easily be much cheaper in the end to buy a new one!