If not already ... You'll need a multimeter with continuity and resistance (Ohms) check function, as well as DC Volts.

You may also have fault, or the accident may have induced a fault, with the bulb-out sensor.

You have pretty good wiring diagrams for 240 here at

http://www.volvowiringdiagrams.com/?dir=volvo/240%20Wiring%20Diagrams

You'll want the "Volvo 240 1988.pdf" Though if your model is a half-year, like it is a 1988 model, yet built in late 1987, you could have circuit layout variance.

Follow what Onkel Udo II recommends in his response to your post.

At what speed did the impact occur? You may have damage at and around the impact point at the North American drive side front corner. You may need to remove the works, the battery, and such to inspect the insulation damage, conductors damage (wire severed or pulled out of the termination) like what may be a faulty connection to ground to the head lights.

Yet what you describe, "nearly all lights do not work unless the turn signal is pulled back to activate the brights. (this includes the radio, ALL interior lights, brake lights, hazards, of course head lights) but it does not include turn signals, and until recently the rear fog lights worked if the headlights switch was turned on."

If the impact was at a high speed, other components may have moved around. The aforementioned bulb out sensor ... yet you have the high/low head light relay in the area Onkel Udo II mentions, a host of wire harness interconnects, certainly connections to ground for left side headlights and more in the area.

Of, if the damage at or after the impact creates shorts to powered conductors (wires), like a chafe to the insulation, other shorts may follow.

It would help if you could post images of the damage, perhaps. Yet we can respond and speculate. I'm sure Art B. may have some useful suggestions for you.

SO, with your trusty multimeter, you'll have to perform continuity checks to verify a de-powered circuit has, or does not have continuity, on a circuit that is not performing as it should. Though a simple visual inspection around the damaged area may reveal something useful in your diagnosis.

Else, other may chime in with more details of how to perform your circuit diagnosis. Please follow Onkel Udo II's suggestions.

Questions,

Thank you,

Sleepy Caturday.

Just some suggestions on strategy:
IMHO, the most efficient use of time is to check the easy (obvious) things first as already suggested. Then pick just one of the symptoms, which ever is easiest to get to, and work on that. Solving one may fix the others also.

Repair your car, then check the lights - as mentioned in the other post, you have a ground problem.

See the FAQ - A bad ground in the left front fender will cause a 7 series to stall if you use the high beams!

Keep in mind, plastic mounted items such as headlight bulbs need a ground wire, metal mounted items may not.

Damage to your left front fender probably disconnected the ground bus from the body of the car. Also, you might check your engine ground straps as well.

Pretty sure you have a major grounding point and a distribution block for power in front of the driver side wheel well...check both of those right after you actually remove the appropriate fuses from their holder, clean the ends, clean the holders, inspect the fuses for eroded ends, re-tension the fuse clips and re-install the fuses.

I would bet money that it is a ground wire or fuse(s).