Jeff is correct about the 2-speed switch, but the issue with turning them off is most likely the control relay on the right fender. (I almost wrote driver's side, oops)
This is what I grew up with as a rachet relay. Every time it is signalled by the driver it snaps down and flips the mechanism on or off. As they get old they tend to jam a little bit and will not always change position. If you take off the cover you can see what I mean. Generally they have one position that doesn't want to switch from. Mine currently also has occasional problems turning off.
New relay for this problem.
Allen