Alex i tried what you said but still same
We will first of all need to check some things on the backpack charger and the charging socket to eliminate any faults on these items.
Plug the charger into the mains 240v supply, but do not connect to the backpack charger socket.
Does the green light show on the CHARGER unit?No - It appears that the charger may be faulty.
Yes - Now plug the charger into the backpack again
Does the light on the CHARGER go red or does it stay green?Yes, it goes red - This most likely means that the issue is a faulty pump
No - it stays green - You will need to check the backpack charger socket pins for corrosion, to eliminate this as an issue. Please look carefully at the outer two charger socket pins (not the middle one).
Is there any sign of corrosion on these charging socket outer two pins?Yes there are signs of corrosion - Please clean off this corrosion with sandpaper to ensure good electrical connection. Now plug the charger into the backpack again. Does the light on the CHARGER still stay green or does it immediately go red?
No - this most likely means the pump is at fault.
Yes - in that case there is most a likely a break in the wiring or a loose connection which is not allowing the battery to be charged. (There is a small chance that it is the charger that is faulty and if no wiring break is found then this would be the case)
No corrosion at all - - in that case there is most a likely a break in the wiring or a loose connection which is not allowing the battery to be charged. (There is a small chance that it is the charger that is faulty and if no wiring break is found then this would be the case)
How to check for loose/broken wiring:First remove the base from the backpack (6 screws) and also remove the battery tray (4 screws) - now carefully look for any broken or loose wires - if found this may be the cause of the issue.
Th above logic flow should help you identify the issue.