so i am new here and hope I am posting in the correct place for my question
My headlights both work on low beam..... however when I switch to high beam, the high beams both light up. Along with the driver side top low beam. ..... but the passenger low beam doesn't light. So on hi beams 3 lamps are lit.
have not done any trouble shooting yet. hoping somebody may have had this problem and steer me in the correct direction.

 

hi if anyone's got a schematic of the headlights that would help! was hoping some one else had had the same problem and I could be lazy

 

Schematics for the 1990 G20 are available here for the 5.7L (350). Stuff like headlight circuits, the engine doesn't matter.

https://charm.li/Chevy%20Truck/1990/...V8-350%205.7L/

Headlight circuit diagram 1 of 2:

https://charm.li/Chevy%20Truck/1990/...%201%20of%202/

Part 2 of 2:

https://charm.li/Chevy%20Truck/1990/...%202%20of%202/

 

Do you have separate high and low bulbs/lamps, or is it one? If its one, then I would suspect something going on in the connector for the headlight that is acting up, since it appears light green is the wire for the high beams, and tan is the wire for the low beam. Maybe a short in the connector for that one headlight assembly?

 

has 4 lamps. The bottom 2 are high beams with 3 wire plugs.......the top two are low beams with 2 wire plugs.......the odd thing is low beams work when on low beam......but when switching to HI beam the passenger side low beam goes out. while the driver side low beam is on so only 3 lamps are lit

 

sorry didnt mention this....passenger side orange marker lamp in the grill is out too