Headlights - only high beam working

[Jezza_hr]

I'm probably going to end up answering my own question eventually, but if anyone else has had this problem before, it would be good to know of one key thing to look at to get it solved.

So, lately, when it's been cold and wet outside, my headlights have been playing up. When I get in the car my high beam indicator shows on the dash without the lights even being switched on. If I flick the high beams to on (without turning the switch to pop up the head lights) the headlights come on. If I just switch the low beams on then there's no light at all, but the high beam indicator stays on.

It would seem that the high beams are constantly grounded somehow. I'm guessing it's either the stalk or the dial switch? But if anyone has any other ideas, please let me know.

FYI the lights run on HID and they have for about 3 years.

[Uzelac]

Get the switch out, and if continues you know it ain't switch.
If it gets normal, than it is switch .

[Jezza_hr]

EDIT : Ignore my ignorance. Yep, removing the switch should help narrow it down.

[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