450sl wiper speed

I have a 450sl 1980. The first wiper position does nothing, second postion is slow speed, third position is fast speed. I think the first postion is supposed to be intermittant but don't know. Any help in fixing this would be appreciated. What controls the wiper speeds and where is it located?

Thanks,

Jim

[cbdo]

The first position is intermittent; the delay is fixed--there's no separate control to adjust it. Second is continuous slow, third is continuous fast. I'm sure there's a single piece delay module, but don't know where it is.