I've had several turbo Dodge cars from the 80s that from time to time had problems with the wipers not working for unexplained reason now and then. This includes the Daytona, Laser, Charger, Omni, Caravan, Horizon, TC3, 024 and others that use this same style wiper motors with the mount that has the integrated ground strap. It was a guessing game and a bit of luck before I discovered the problem and came up with the fix as to if the wipers would work when needed or quit during the very time they were needed the most, in a rain storm!
There are several problems that might be causing your problem that might not be this problem, but it takes only a few seconds to test for the problem I am often finding and if your test is positive, the fix is quick and cheap. Why replace a good wiper motor when you don't really need to? BTW, replacing the wiper motor will not fix your problem in this case.
First of all, the problem has nothing at all to do with the motor! The problem has to do with the design of the motor mount and how the factory engineers designed the ground strap for the wiper motor. Since the motor is bolted to a metal plate that is bolted to the cars plenum with rubber isolator grommets, they had to also provide a means for a solid ground for the motor. The ground in this case is a copper or steel strap that is riveted to the mount and then passes UNDER one of the steel inserts of a rubber mounting grommet. Over the years, the strap and the steel insert create a poor ground connection that acts up under a high current demand, such as when the motor is running and the area is damp or soaked from rain.
To test to see if this is your problem, just turn on your wipers on a low or high setting (but not intermittent) and attach a piece of wire from the wiper motor gear box housing to a good ground. If you wipers then begin to run, you have a ground problem between the wiper motor mount and the wiper motor casing.
The solution is to add an additional heavy ground wire. You need a pretty good wire here because the motor does draw quite a bit of current. The wire I used was a bit over-kill but you get the idea.
I bolt the additional ground wire to the back side of the bracket, using one of the wiper motor mount bolts.
The other end of the additional ground wire goes under the nut for the lower mounting stud. That is where the factory ground strap is located. Honestly you can attach the wire to any of the mounting studs.
Once installed, you just re-install the wiper motor and it will start working reliably again.