Definately worth a shot to correct yourself before you spend big money on the wiper switch. I just did this last week. I just picked up my new to me car in CA. Hadn't seen rain in years. Doubt the wipers were uses all that much if ever in that time. The intermitant rheostat worked so in my mind the motor and relay were good it was just the switch that needed cleaning. I also found that by pushing forward and wiggling on the stalk I could get the wipers going for at least a little while.
Remove steering wheel and cover. Careful with the cover. There is a good article in tech section on this part. Once cover is off you can see the wiper switch plainly. Inside the switch are two sets of contacts for park and washer functions. Basically two sets of fingers that are pushed together at the correct time. I was very careful not to bend these. The main contacts for the three wiper speeds are the side of the switch closest to the column. There are a couple of long contacts and three round contacts. Mine were corroded over with lots of dust and what appeared like varnish.
Anyway I first sprayed with electrical contact cleaner. I held a towel behihnd the switch to keep from getting cleaner on the rest of the car. Then I went to q-tips and finally ended up scraping the contact surfaces with a small screwdriver followed by more q-tips loaded with electrical contact cleaner. Once all the contacts were clean my wipers function 100%. It took maybe half hour start to finish.
Here's a shot of the switch from the top. You can see the contacts on the left inside the switch and also the 'fingers' that create the park and wash functions.
Here's a view from the bottom. You can better see the contacts that need to be cleaned.
One more shot showing the park and wash contacts.
-J