99 delay wipers

When i have the delay wipers on the lowest part of the delay range they are the same speed as when i have them on the high range.... but it move it to the actual LO and HI options they have a huge differnece its just the part where its the delay range that doesnt seem to be working. DO i need a new multi function lever and if so how do i install it and where do i get one at a reasonable price
??
Thanks Derek