91 honda accord ex stalls when i turn on lights, turn off lights run good.what causes this?

91 honda accord ex stalls when i turn on lights, turn off lights run good. What causes this?

Sounds like the battery is low. WHY it's low is the question. The alternator may not be working, or the battery could be shot.

Start by checking the cable terminals for corrosion or loose hardware, and correct as necessary.