HID Fog Light Question

first i installed the HID kit about 8-9 years ago and the fog light MOD.to turn on without the headlights and had no problems i had to replace the bulbs in that time which is not the problem but now i having this problem one light was out so i changed the bulbs and still no good so i tried the the bulb on the other side and it worked so i checked the wiring and all good so i changed the ballast and it worked the a few days later same thing then it was good for months but now it happens on both sides one might be on then i hit the switch a few times and they both are on or the other side goes out and the other one comes on but all the wires are good but the weather is very cold now but it been cold the last 9 years or can it be the switch any suggestions

Thanks