Geoff there are two independent mercury switches in the lid. One senses when the lid is closed (you need to bypass this one) the other senses when the water level float in the agitator touches the black button underneath the lid. If you open the lid with the lid switch bypassed the mercury in the water level switch falls down to the bottom of the switch via gravity and the machine thinks the proper water level has been reached. You can set the water level to what ever you want and when agitation begins you can then open the lid.
In summary, with the safety switched bypassed, if you open the lid when the machine is filling it will simply start to agitate. If you leave the lid closed during the fills the machine will start to agitate when the proper water level is reached.
In my AMP I start the washer without any clothes in it with the lid closed and I let it fill for a minute. Then I open the lid and let agitation begin and add the detergent to mix in with the water with the agitator going. After 20 seconds or so I push the dial in and add the clothes and close the lid. I pull the dial back out and the machine fills to the proper level. When agitation begins again I can open the lid to watch the action.
In summary, with the safety switched bypassed, if you open the lid when the machine is filling it will simply start to agitate. If you leave the lid closed during the fills the machine will start to agitate when the proper water level is reached.
In my AMP I start the washer without any clothes in it with the lid closed and I let it fill for a minute. Then I open the lid and let agitation begin and add the detergent to mix in with the water with the agitator going. After 20 seconds or so I push the dial in and add the clothes and close the lid. I pull the dial back out and the machine fills to the proper level. When agitation begins again I can open the lid to watch the action.