Use something called Nikwax TX Direct. The water-repellency finish is worn off. What this means is that your jacket is still waterproof, but it cannot bead water. Hard to explain without showing you, but TX Direct will fix it.

Actually I have an excellent answer for you. I purchased the Mtn Light jacket in 1991 or 92 and the repellency went away as well after a few years of use. I called the company and found that they have the best warranty out there. I sent the jacket back to TNF and 3 weeks later they had sent me a brand new jacket. A few years later, that one went out as well and I sent it back too. I now am on my third incarnation of the Mtn Light jacket that I had originally purchased in 1991. This is a fantastic company who really stands by their product. I can't say that many companies do the same these days. The warranty information is found here: http://www.thenorthface.com/en_US/contact-us/warrantyproduct-guarantee/. Good luck to you!