Cant say specifically but this is a situation where a multimeter comes in very handy.
You can check whether the lights are receiving 12 volts, and also whether they are earthed to the body to ensure a circuit back to the battery. Poor earthing is a common cause of faulty lights. If there is a power supply problem you can test back through the wiring circuit, check switches etc to locate where the problem lies. It can check if bulbs and fuses have blown (a visual check is not always reliable.)
If you havnt already got one you can buy a suitable electronic one for about £7. You will find lot of uses for it around the car and home over the years. Only yesterday I found two AA batteries in a drawer. Tested them , One was 1.6 volts - ie new, the other was under 1 volt and should have been thrown away , I mean recycled.
These little savings add up
