B.  The led bulb contacts may not be making solid electric contact with metal contacts in the socket.  Check the contacts on the bulbs and socket.  Realign or adjust as needed.  Reseat the bulb.

C.  Are you sure the filament bulb still works?  Often in the process of installing, you can pop a fuse or lose a wire/connection to the socket.  Always use the glass bulb or a voltage meter to verify there is at least +12 volts to the socket. 

D.  In some vehicles some automotive circuits will not fully energize the circuit, or pulse current to the bulbs to check to see if the bulb is burned out.  Since the leds draw 90% less power than the glass bulbs, these circuits do not switch on full voltage , or will not stay on when the led bulb is inserted.  This can be corrected by installing one 6 ohm load equalizer across the circuit at each led bulb.  This will add more load to the circuit and make the full 12 volt power switch on.   In this instance, the glass bulb will make the power switch on, but the led bulb by itself will not make the full 12 volts switch on.  

This creates the illusion that the led bulb is at fault when in fact there is not 12 volts at the connection when the led bulb is inserted.

B.  The led bulb contacts may not be making solid electric contact with metal contacts in the socket.  Check the contacts on the bulbs and socket.  Realign or adjust as needed.  Reseat the bulb.

C.  Are you sure the filament bulb still works?  Often in the process of installing, you can pop a fuse or lose a wire/connection to the socket.  Always use the glass bulb or a voltage meter to verify there is at least +12 volts to the socket. 

D.  In some vehicles some automotive circuits will not fully energize the circuit, or pulse current to the bulbs to check to see if the bulb is burned out.  Since the leds draw 90% less power than the glass bulbs, these circuits do not switch on full voltage , or will not stay on when the led bulb is inserted.  This can be corrected by installing one 6 ohm load equalizer across the circuit at each led bulb.  This will add more load to the circuit and make the full 12 volt power switch on.   In this instance, the glass bulb will make the power switch on, but the led bulb by itself will not make the full 12 volts switch on.  

This creates the illusion that the led bulb is at fault when in fact there is not 12 volts at the connection when the led bulb is inserted.

With many flashers, led bulbs will cause the turns signals to flash rapidly, or not flash at all.  

If using led bulbs for turn signal applications, or in vehicles with bulb-out warning systems, like Mercedes, BMW and others, you may need to add load equalizers.    

For led turn signals, you can change the flasher out using one of our new patented combination led/oem bulb flashers.  Most electronic flashers are not the same as an led flasher.   Many electronic flashers do not necessarily work with led bulbs, unless they are led flashers.

If we do not have an led flasher that matches your flasher, use two 6 ohm equalizers for two front, or two rear led turn signal bulbs.

Place one load equalizer at each led turn signal bulb location.    For turn signal led bulbs, the equalizer must be spliced across the - ground wire and the + turn signal wire feeding each led bulb.

More details on load equalizers and led flashers can be found at:    

http://www.autolumination.com/equalizers.htm

http://www.autolumination.com/equalizers.htm

http://www.autolumination.com/equalizers.htm