APU Runs for a few minutes, shuts off with red ENG light

Had shop replace coolant "y" fitting by the firewall today. Apu would crank then shut down with red triangle. Sure enough, coolant lines to apu were turned off. Two yellow valves on passenger side firewall. Follow coolant lines down and they are right there. Turned both of those back on, bled air out by just slowly loosening radiator fill cap and vroom vroom. Back to running again