I am trying to quickly order a LED tail light bulb for my 04 low rider and there is some confusion as to the correct bulb. To me it looks like a 3157 but most searches state other results such as 1157 etc. Cant seem to cross the HD part number. I took the bulb out and can find no markings on it. Am I correct assuming it is a 3157 before I click "Order"?
Also, if I purchase LED turn signal bulbs, will I need to order a different flasher relay? Is the turn signal bulb an 1156? 3156?
Thanks a Lot!!!

 

http://partsfinder.onlinemicrofiche....TURN%20SIGNALS

Don't know about a flasher relay but you may need a load equalizer.

 

Awesome Nevel! Thank you very much for the link. It does cross to a 3157...don't know why HD cant just use the universal bulb number? On my car when I installed led turn signals I had to purchase a different flasher relay so they didn't hyper-flash (flash very rapidly)...not sure if that is the solution for the Harley.

 

I got my 3157 LED tail light and it is an excellent upgrade. It is substantially brighter both as a running light and brake light. Just for kicks, I installed the second bulb in the front blinker / marker and the blinkers flashed very rapidly so I called the dealer and they sell a flasher relay that will work for the led bulbs. I am going to upgrade those and in the rear I am going to put a red lenses and get them to work as both marker lights and blinkers rather than blinkers only in the rear. I will post pictures when done. I did take some pictures with my SLR set to manual exposure for all shots with both the incandescent as a tail then as a brake and then did the same with the LED bulb. Pretty dramatic difference and I particularly like how rapidly the LED switches from marker to brake and back.
These are the bulbs I purchased;

 

Different flashing mechanism from auto to a FI Harley. Autos (some not all) used a bi-metallic strip and both sides heat up at different rates causing the strip to bend. The strip also conducts the electricity and so performs the function of a switch.. heats up bends away from the contact, circuit is broken-light goes off, cools down and touches the contact again.. light go on.

The EFI bikes with the ECM, you are basically providing a signal to the ECM to tell it to pulse your turn signal, which it does with solid state circuitry (IIRC). It also measures the current required to turn the bulb on, and if it's not enough, if will flash faster as a warning. ... So the load equalizer ( just a power resistor) in parallel with the bulb pulls the amount of power required for the ECM to think it's okay.

By the way, the 'flashing faster' is the same result for both auto and ECM bike. In the case of the auto, the faster flashing is caused by the bi-metallic strip not moving very far away from the contact, because it's conducting less power because of a missing or 'out' bulb. Moves less = moves faster = faster flashing. Harley simply mimicked that same 'result'.

 

Go bold on the tail light/brake light and get the BAL-1 for your Dyna, cage drivers will get off your ***. You can see that light 1/4 mile back in the daylight.