Try this: viewtopic.php?t=39890
Most likely it's the motor or the connector. The connector is prone to get full of water and dirt and corrode. The wiper timer relay for intermittent is in the wiper switch itself.
If you want to test the switch, you can unplug the connector that goes to the switch on the steering column, then short the following pins to activate the different modes:
1 and 3 = high
2 and 3 = low
2 and 4 = intermittent
Refer to pic to see which pin is which.
If in the unlikely event the switch is bad, you can have the spare I have for the cost of postage.