This is a somewhat complicated problem so the answer is not very simple.
An Osmolator made before 2009 used an 800mA PTC as a sort of circuit breaker for the pump, since 2009 it is 1200mA as in late 2008 we requested the pump manufacturer customize the Osmolator pump with a double o ring seal to increase the durability, the added drag needs more mA of power to run the pump. What you are seeing is more than 800mA is required and as a result the PTC is breaking contact. The key to solving this is to get the draw below 800mA, this means clean wiring, no corrosion, a 9V power supply, the original was switchable 9-12V and 9V will reduce the mA consumption, of course the pump also runs slower and a good working pump, the higher the head pressure the less mA draw as well. If all these are in order it should work, long term if ignored a transistor will overheat and damage the controller irreparably. If it was me, I would strongly consider just replacing it when the big black friday sales roll around as with the age, more issues are probable in time.
