Try cleaning your windshield with comet or some other type of abrasive
cleaner.  Sometimes the built up road grease creates this condition.  On the
'00 rig, we found that overspray from the nearby construction project was
causing  the wipers to bind.

Here are some messages I posted to a forum several months ago.  You may find
some of the information useful.
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Hello, this is my first time posting to any forum. I'm pretty new to the
world of car care as well. Until recently, I've always been the type just to
wash & gloss when I had the time. I never really made any effort to research
products before I used them. I just usually went with whatever I found on
sale at Walmart.

Well, I bought my first brand-new car, a 2003 Subaru Forester. So I felt
inclined to change. Now I try to buy only the best products for my new baby.
In my quest to find the best. I found myself reading about many products to
renew and restore. So I decided to make one of my older vehicles, a 1992
Ford Festiva. a test subject.

My first project is to renew the glass. The windshield is in poor condition.
It has over 10 years worth of water spot buildup and various nicks. It has
an unremoveable haze that contrasts the path of the wiper blades. Even new
wipers tend to skip and leave a fog which makes driving in the rain very
difficult, especially at night. For me, this is a situation of repair or
replace.

Being the frugal type, I decided to take the low cost approach and test
various glass care products I had around the house. I tried Windex,
GlassPlus, Stoner Glass Cleaner, BarKeeper's Friend (a mild abrasive for
glass), and even full strength vinegar. Nothing made a difference. Nothing!
So I decided to go-for-broke and try any chemical I thought might make an
impact. These failures include, mineral spirits, acetone, gasoline, and even
laquer thinner. Again, nothing worked.

I started searching the internet for glass restoration products. I realized
Janvil, Diamondite, and Autoglym products were worth more research. My next
step was to look in various forums for recommendations on these products. I
was reading along when somene posted a very small comment. It read, "I used
detailing clay and had good results." That was it. Nothing more just the one
line. Since I had a small bar of detailing clay that had come with sealant
kit I had recently purchased for my new car, I decided to give it a try.

Detailing clay is used to pull contaminates from automotive paint prior to
compounding, polishing, or glazing. It usually comes with a special
lubricant which makes the clay slide across the paint with less drag. I
applied the lubricant and repeatedly pulled the clay in one direction across
the glass. The clay just seemed to float on the lubricant. I couldn't feel
it actually make contact with the glass. So I wiped the lubricant off the
glass and started over leaving the clay slightly moist. This time I noticed
a definite drag. As the clay slid across the glass it made a faint sound
similiar to static electricity in a freshly laundered load of sheets. I
thought nothing of it and kept dragging. To my suprise, the noise got
fainter and fainter until the clay made no noise at all. I also noticed the
it barely had any drag and was slick from sliding on the glass. So I stopped
and felt the glass. It was as smooth as...well, ...glass! I clayed the
entire windshield and finished up by removing the residue with Stoner Glass
Cleaner.

To my delight, except for the nicks, the glass is completely clear. The
water spots are gone. The haze is gone. And my newly installed wiper blades
dont skip or leave any fog. The glass has a gloss I haven't seen in years.
It was like having a new windshield!!! TOTAL SUCCESS!

The whole claying process probably took 20 minutes. Its well worth the time.
I hope this message helps anyone looking for an easy quick fix to restore
their vehicle's glass.
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I think RainX is a terrible product!  I DO NOT like the way it causes wiper
chatter and skipping. It may work fine at high driving speeds, but at low
speeds the generated headwind isnt sufficient to carry the water droplets
off the glass. The water beads TOO WELL on the glass leaving distinct wet
and dry areas. The droplet build-up necessitates wiper use which causes
blade chatter on the dry areas. Unfortunately, glass treated with RainX will
never again behave like untreated glass. Nothing removes this stuff. I've
spoken with the manufacturer at length about this effect. They offer little
help and seem genuinely unconcerned. Frankly I'm suprised the product has
had the success it has.

From what I've been told RainX is a proprietary silicone formula suspended
in a carrier alcohol. Appied, the alcohol flows the silicone into the
microscopic pores in the glass and then evaporates, leaving the silicone
behind to fill the pores.

For what its worth, here's a list of chemicals I've used with no success:
mineral spirits, acetone, laquer thinner, unleaded gasoline, isopropyl
alcohol, a pressure washer, Tide, Dawn, and per RainX tech support - Bar
Keeper's Friend. I havent been able to find anything to remove it. (In
retrospect I shoud have tried denatured alcohol, but I didnt think of it at
the time.)

I suppose many people must find RainX a useful product; otherwise it would
have dissappeared long ago. Personally I do not.

Future users should use caution because its a one way trip. Personally I
dont think its worth the risk.

Hope this helps!