Wiper only works on one speed

Here is a pic of the wiper motor. Does this help? Am I missing a ground wire?

This is exactly like the motor in my 73 Dart. The Dart used to have a two speed switch, but the post broke, and I replaced it with a three speed switch (only one I could find at the time that fit the plug pattern). The dart works on all speeds, but the lowest, that is supposed to be the intermittent, just goes at a slow speed, and the middle speed is slow and the third "click" in the switch works at normal high speed.