I have a 99 4runner sr5 sport 4wd. I’ve had it about a year now and ever since I got it it’s done this. When I have the headlights on and pull 2 window switches at a time the headlights dim. As soon as I let off the switches the headlights go back to normal. I knew the truck would need some work when I bought it, and now I’m getting around to it.

so my question is: Is this a known issue? Is there a fix for it or is it just something that happens. There are no other electrical issues with the truck. Thanks

 

Not a known issue.
Make sure battery connections are clean as well as all grounds.
Use sand paper or emory cloth.

 

Is that with engine on or off? If off, what happens with it on and vice-versa?