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89 F150. The wipers start & stop on hi. Anyone have any idea. Thanks, Chuck
You didn't say if you have the Interval Wipers or just the Hi and Lo wiper system.
(Assuming the linkage is not binding)
I believe the wiper motor is the same for both systems.
The wiper motor has a high speed winding and a low speed winding. In either system, if the Hi speed circuit has a problem, the Wiper Motor or the Wiper switch is bad.
If you have the Interval Wiper System, in Hi mode, the Wiper Control Module is bypassed so the module can't be the problem.
On the 89, to find the Wiper Control Module, look under the dash at the wiper switch and follow the harness. It will lead to the Wiper Control Module which is bolted to a bracket near the emergency brake area.
Please excuse the ignorance of an infrequent user here. In your post I followed, the words, control module are highlighted in blue. I clicked that, thinking it was a link to more info on that module, and found it to be an advertisement link. I din't realize they(ads) were embedded in threads!