[orbot]

Are you sure its bad, check the plug on the firewall, mine fell off (disconected) and i thought i had a bad selector valve lucky me i already had a spare then found out it was the plug... anyways the only way to do this with a mechanical pump is to do some plumbing and with some shut off valves where you would do it by hand, on the other side get electric pumps and a double throw relay a switch on the on side will power one pump if you put the switch on off it will power the other one.