HVAC Questions? Ask an HVAC Expert for Answers ASAP
If the display is blank with new batteries in, then there are only two possibilities:1. There's no mains supply to the unit;2. The unit is faulty.If you have the means of testing the supply, then that's the next step. Otherwise you'll need a heating engineer who's capable with electrics. You could replace the Digistat, but if you find out later that there's no supply then you'll have wasted your money.