Headlights - only high beam working

[jondee86]

The AE86 has a constant 12V supply to both the high and low beam
filaments in the OEM setup. The filaments are turned ON by connecting
the filament to ground. The high beam indicator light is connected to the
low beam circuit on the ground side of the filament, and held OFF while
the low beam filament is grounded.

When the ground is removed from the low beam and applied to the high
beam (as the dip switch is moved) the indicator now receives 12V and is
illuminated. Kind of counter intuitive, but that is the Toyota way

The behaviour that you have described indicates that there is a break in
the low beam switching circuit. There is no ground being supplied for the
low beam filaments when the switch is in the dip position. Check to see
if you have 12V on the Red-Green wire that connects to pin B6 on the
headlight switch when the switch is in the high beam position.
The other end of this wire should be on pin A11 in JB3.

If you have 12V at B6, moving the switch to the low beam position should
provide a ground for B6, turning the low beam filaments ON and the high
beam indicator light OFF. If it does not, then the problem is inside the
switch.

Cheers... jondee86