I have a problem with a new (used) Nissan variable speed wiper switch. I have a 2000 Frontier that did not come with variable speed wipers. I purchased a switch from a salvage yard and installed it. I still have the two speeds working (high and low) but now variable speeds. Any thoughts on what the problem is? Everyone I have spoke with says that motors for this model are all the same...so the switch controls the speed correct? Can anyone help? Thanks Steve