What's up all, first time posting on the forum & excited to be here!
Hoping someone has run into this and can give me some much needed help.

1985 4runner, pretty much gutted interior as I am working on the build.
It has a fun little trick that has happened since I've had the truck.
Rear window works decently well, all things considered. (newer tailgate from an SR5, was on it when I picked it up)
However, when the rear window is up, and I turn on the marker lights or the headlights, it immediately rolls down.

I then disconnected the window switch with the window up, and turned the headlights on, and the window did not roll down.
Wishfully thinking, I hoped it was the switch. I replaced the switch with a new aftermarket one, and no dice. Window still rolls down whenever the headlights are on.

Hoping someone has run into this and can point me in the right direction, any help is GREATLY appreciated!

 

That 1985 is hopeless. Sell it to me. :
Welcome to the forum!
Does it happen even with ignition off? Need to narrow down becauase there are 2 power sources for window control.
Does it happen only from window up? Never rolls up from window down?
​​​​​​Does window work normally when lights are out?
Possible short between lights wiring and window wiring? (left side body cavity). With lighs out in the dark, have someone cycle window up/down while you look closely at lights if they blink, or better yet, monitor voltage on tailllight positive wire.
How window control works with schematic here:
https://www.yotatech.com/forums/f116/how-rear-roll-up-window-works-304516/#post52399326

 

Hi there! I am having the exact same issue. My rear window rolls down automatically when the headlights are on. Or even running lights at that. It operates normally when the lights are in the off position. It does not roll down when the key is in the off position. Any advice would be appreciated!

edit : 1985 4runner 22re

 

With lighs out in the dark, have someone cycle window up/down while you look closely at lights if they blink, or better yet, monitor voltage on tailllight positive wire.

 

Since you mention this only happens with the ignition on, the relay module isn't powered off the ignition circuit, so only the rear door switch would work. There's likely something amiss with the switch in the dash, because it won't work w/o the ignition on (unless you've jumpered the pins together like shown in this video:

It may be that the switch illumination wire and the down contact wire are shorted together or have been swapped.