I was working on a D&B chiller 100 tons. Installed new condenser water pump. And every thing looked good bumped the pump and corrected rotation. Turned it on and nothing. Started trouble shooting every open was through the board and I almost condemned it when I decided to tap on all the relays. Still no luck. There are little fuses in that board and I ohmed out the suspected one checked good. Pushed on them all and after I pushed in three or four the unit came on. They are black with two little wires poking out of the bottom. Might try it next time and hopefully save yourself a trip.