good day Theo: The following is a copy from you earlier posts.
The switch selects either 120 or 240 volts its on the front panel above the sockets however the switch is loose inside, it does nothing.
Looking at the picture of the front panel I do not see a switch above the sockets. But then that area is not entirely clear.
One of your earlier pictures shows a simple toggle switch to the right of the blue plug. It shows 120 volts on one side and 220 volts on the other side. Can you explain that to us?
Yes, the item pictured last is called a full wave bridge. It converts AC voltage to DC voltage. The DC voltage goes to the brushes,which in turn feeds voltage to the field winding's. The field winding's form an electro/magnet. When revolving, the magnet excites the L and the R winding's. Since the L/R winding's have already showed 120 volts each the bridge is not the problem.
The problem will be correctly reinstalling it back into the system. Show us how you plan on doing that.
From your last post: There are 4 wires coming from the alternator. It sounds like you are you referring to the L/R winding's. You have already established the resistance of the two, check them out.