I was driving my family Mercedes Benz S320 recently and a warning sign just pop out of no where from the central instrument. It said " TURN SIGNAL L, SUBSTITUTE LAMP ON!"
Obviously one of the turn signal had kaput but what puzzle me is the "SUBSTITUTE LAMP ON!". I had been driving for more than 20years and had never encounter a substitute lamp when a lamp went busted.
So I stopped the car and put on the emergency lights. If you see the picture above and the picture below you will understand. The above pic is showing how the car is using the reverse lights as a substitute for the busted indicator!
If you look at the picture below you can see the differences in the indicator locations. The left side is using the reverse lights as left indicator. The one on the right is working fine so it's blinking from its original location.
Here is the busted bulb that I took out from the car and had replaced a new bulb from HuaHo Kiulap. It cost only BND$3.00