Volvos come with a rear fog light and it's switch is right next to the headlight switch. Front fog lights require another switch, if your car didn't come with them already installed. I have never heard of a computer mod for adding for lights in the front, sounds like you have been talking to too many wives.

Make sure your rear fog light works, it's in the driver's side tail light cluster. Next to the brake light. It is actually the same size bulb as the brake light. Try only to use the rear fogs on really foggy days/nights. They are very bright to those following you and drivers assume you have your left foot on the brakes.

Klaus
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95 854T, 88 780, 88 245, 01 A4 Audi