There is a easy way to fix it you can send in you car to a repair store such as auto tires they can fix your windshield for cheap or you can do it manually for free.
Find the leak and repair it with a compression or push-in fitting.
ughh i have the same problem. you need to fix the windshield wiper motor
You need to find and repair the vacuum leak.
The acturators that control the defrost and vents often become inopterave because the mechanical link from the acturator to the divertors breaks. You can see if this is the porblem by looking just to the right and above the gas pedel. I have just tryed adding a screw and some glue to see if that works. The only problem is, that I had to remove the entire dash to get to the diverters and acturators. About 4 hours so far. But I am a shade tree machamic.
I'M NOT A MECHANIC but I know on my 1995 XLT when I select defrost the air conditioning system compressor will cut in and out in order to de-humidify the air. I was just wondering if your A/C compressor pulley turns or if something is seized up ?
Check under the hood for a broken or disconnected vacuum line.
you need to replace the vacuum.
Could be a vacuum leak "defrost" is the default position of the system Check vacuum lines and motors under the dash
Have alternator checked. Should be getting 13-14 volts running. If not that, have battery tested.
First you have to diagnose what the problem is before you can fix it.