3 swicthes on the wall!

There is 3 switches on the wall , when switching one on, a red light flickers on the circuit,and a umming noise comes from boiler, but when switching the other two on nothing happens and also the two green light don't come on niether,and there's no hot water,

HELP!!!!

Hi
If both lights are off and the overheat reset doesn't have any effect, it's usually means that the water level in the top tank has gone down.
Simply lift off the white lid and have a look inside. The tank should be about 1/2 full (or at least covering the smaiil black float at the front of the tank).
Fill the tank back up to this level and it should rectify the problem

This link -> Pulsacoil 3 Repair has information on the guide and you can request it for free.