I have a 98 4runner. Every so often when the turn signal is engaged the headlights go off for about a second. Has anyone seen this and know where the problem may originate?

The problem is not easily reproduced so it could be that I slightly turn the headlight knob when using the turn signal. In which case the problem is between the seat and the steering wheel.

Thanks

 

You hit on my first guess.
I was once halfway up 8 miles of cliffside steep uphill switchbacks (extraordinarily beautiful country, British Columbia) driving waaaaay too fast late at night in a 3000GT when the lights went out! I panicked, but then hit the light lever to pull it for passing lights and they worked! So I held the lever for a sec and slowed down then realized that the fog lights had gone out too, and the lights do work, soooo... apparently I had twisted the knob when I flipped onto brights or something. I turned them back *ON* and all was fine. I drove slower after that...

But another possibility is you have a bad bulb or socket, and it makes a short once in a while. Check em all and clean em good. Can't hurt anyway.