The tiny bulbs in the rocker switches are the same as those in the warning lights. Many times the instrument cluster has installed a bulb at every little square, even those not used in your specific model. E.g. the green OD light in an autobox car, the amber OD light in a stick shift car, the choke light in a FI car, there may be others. Get some from a cluster at a recycle (pc junk) yard. The white light over the rear ash tray has one, too.

I have bitten the bullet and keep 5 or 10 in Bob's Garage Volvo Parts Department. Long drive to dealer.

Rear fog lights became standard in 1986, with the advent of the 3rd brake light. The upper inner light which is the brake light on 1985 and back became the rear fog light. The lower outer on 1986 and on became a two filament marker and brake light. So....

For rear fog lights you (1) prolly don't have factory wire. (2) will need to run new wires. (3) Might be better served to use the switch for front driving or fog lights. The rears are supposed to give a driver behind you in fog a chance to stop before whacking into you. (Houston had a 73 car pileup in a heavy fog last month!)

If you run for heavy lights, use a relay in the circuit. Switch closes relay, relay closes to allow heavier current in heavier wires to power the lights.

The 1986-on models are wired so that the fog lights cannot be on with the headlights off. Plus, the headlights cannot be on if the key is removed.

Good Luck,

Bob

:>)