Greetings,
Discovered the left side low beam headlight does not light up. However, when I switch to high beam all 4 lights are on. What!! Anyway, I checked the fuses. All are good. So any tips about what to test next are welcome.

ok, this is on my 1990 XJS V12 Convertible.

 

It has to be one of the following.

- Fuse 4 in the black fuse panel in the engine bay
- Connectors on fuse 4 or to the low beam lamp
- Faulty low beam lamp.

According to the electrical guide there are 2 bulbs one is high beam only and the other dual high/low beam when high beam is on low is off what you are seeing is the high beam part of the dual bulb.

 

The low beam bulb has two filaments. I believe that the low beam filament is burned out. Try replacing the bulb.

 

Thanks. I’ll test the bulb itself.