Intermittent wipers not working, is there a control box?

[Old65C10]

So, I am working on my 90 Suburban V2500. When I got the truck the Cruise did not work and I replaced the turn signal stalk. I hoped that this would fix the int. wipers also, but I found out the switch for the wipers is farther down in the column.
So, the wipers work on low and high, but not intermittent. This makes me think the switch is OK, but that there is a control module somewhere. Is that true? If so, where is it located?
I am trying to track down the last few little gremlins, I am down to this and the horn.
Any help would be greatly appreciated.