Do you know how old / how long the pH controller has been in use?
And, what conditions it was used under? (under a stand with a sump and plenty of moisture, in the open air / normal ambient moisture, etc.)
Do you know the last time the pH probe was replaced?
Any corrosion on the fittings where the connections are made to the main unit? It looks pretty clean in the picture, but I'm asking just to be sure.
Sorry for all the questions -- thanks!