Just wanted to share a fix. 1991 ranger with no low speed or intermittent wipers; high only. Tested motor, no power to low side. Incorrectly assumed a new switch was needed. No change with new switch, more research pointed me to the wiper control module under the dash. Removed the lower plastic steering panel (2 screws 7mm) and disconnected the plug from what I believed to be the wiper control module, noticed the plug pulled out way too easy. Verified I had the correct module as wipers would no longer work on high. Plugged module back in until I heard and felt that familiar ford connection click and tested the wipers. High, low, intermittent, everything operational. The connector does not have a good clip and must have worked loose over the years. Hope this saves some a little time. I have a used working Multi-function switch for sale....cheap for the Board.

 

Well, look at it this way. If you had taken it to the dealer, you might have a slightly used wiper motor for sale also... Along with a couple relays. You're way ahead of the game at this point.
Good info to pass on!
tom

 

interesting ... just went through this on my f250. learned from searching this site that the wiper control module was indeed a problem area for that model truck (1989 f250 4.9 manual). the module is located under the dash, drivers side, close to the ebrake pedal . the story goes that after several thousand fairly violent releases of the ebrake pedal, the module takes a beating and some solder joints give way.

when i removed the module i noticed, like you, that the connector came off without any struggle at all but i didn't think too much about it at first. opened the module and everything looked just fine in there. put every thing back together but did NOT connect it firmly enough to hear/feel a click. the wipers worked without a hitch for a couple of days but finally, got the same symptoms back that you have already described.

i am going to go back in and go after that connector again, this time looking for that solid click.