Keep getting 04 code on linea 24 drained pump from car tyre type nipple then repressurised exp. vessel (a tiny amount of water came out when i pressed valve,before i re filled,now just air comes out) to 12 psi but when i switch on it comes on for a second or two light green then turns red with 04 code flashing when i put hot tap on it feels like the pump is on but nothing else if i the selector switch on hot water only with taps off the pump gets hot any ideas out there?