I don't know your truck but usually the lack of low speeds is a resistor assembly inside the ductwork that opens up. It drops the voltage to the motor. The lack of park function could be the switch or the motor.
The lack of low speed in the motor that has been seen on this site is for heater/AC blowers not the wiper motors. Wiper motors DON'T have resistors for the lower speed. They use just part of the motor winding for the lower speed.
95 Taurus GL
94 Mark VIII
Seen that problem about a year ago w/my 91. In the helm manual for my truck it says, if the wiper works on high only then the switch is bad. There's no need to check for pwr or a wire going to gnd. It's the switch that has a wiper that runs on a rheostat. The rheostat is taken out of the loop when the switch is placed on high.
Thanks for all the posts on this. I pulled out the delay module and found diode D2 with bad solder joints to the circuit board on the heatsink bracket side. Diode D2 feed the relay that completes the low speed circuit and when the solder joints break, no low speed and no delay. I resoldered all three connections to D2 on the circuit board and added some small wires wrapped around the protruding leads to the relay leads in parallel for extra connections (just in case the PCB joints break again). D2 is located right next to the relay and has a U-shaped bent metal heat sink bracket with two bend tangs soldered to the PCB. After soldering and adding the parallel wires, reinstalled and it works like new. But before I read these posts, I had changed the wiper motor and still had no low speed so was scratching my head thinking it was the switch. Now I have a new motor and 'better than new' delay control module so should be good for many years.
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