The issue is likely that your contacts are pitted, because of the high currents going through. You should install a relay to prevent this from happening. I bought a brand new switch two years ago, and hardly used it, because I hardly ever drive this car at night. So I have not installed a relay yet, and low and behold, even with this new switch my low beams stopped working. Instead of buying a new switch, you can also try what I did. I is removed it from the steering column, and drilled out the 4 rivets that hold it together. Then you can clean the contact, and bend it a little, so it'll work again. After that, I used two nuts and bolts to put it back together. The two biggest rivets I did not replace, the Allen head bolts go through these holes anyway and will pull the two halves together....I hope this makes sense, you'll probably see what I mean once you get in there. I now have a serviceable switch. Good luck
You can get to the contacts without disassembly. The switch has some holes in the sides where you can see the contacts. You can use a thin strip emery cloth to clean them. Open the contacts and instert the cloth. Close the contacts and pull the cloth out. Keep repeating until they are clean.