Hopefully I can help..
The unit in question is the the abs hydraulic/control module..this sends the brake fluid to each wheel..Its quite possible given what you have said as per tapping the unit to switch it off its faulty internally - its made up solenoid valves/check valves/pump motor and are controlled by the abs control module in which you see the large plug connector fit too on that unit.so it possible the unit itself has become faulty internally or the control side of it and will need replaced..but its best to have it confirmed first via diagnostically seeing the abs warning light is on..this will have stored fault codes and will verify if that the case..maybe disconnect that plug connector and ensure first it hasn't suffered from corrosion etc or water ingress problems that maybe effecting things..I do hope this helps..
thank you we will be taken it to are local garage
Hi..there thanks for your reply..
No problem..Please remember to rate my assistance..always much appreciated..If you need to ask anything else then you know where I am..