I, for one, do not understand LED technology and honestly don't have the time to immerse myself into studying yet another subject
when the technology and information is out there.
LEDs are pretty easy to understand if you understand how a "regular" diode works. The only difference is that LEDs light up (LE means Light Emitting) when current is applied to them. If you don't know how a diode works, don't worry, its "magic."
The LED replacement bulbs are typically a group of LEDs with a voltage regulator, to bring the 12v or 24v down to 5v, assembled together and potted. The potting protects against vibration and moisture. Some of the LED replacement bulbs fit easily where the original incandescent bulbs were, while others don't unless there is a lot of room. There are also LED replacement fixtures that replace the original reflector, lamp, and lens assembly.
The LED replacement bulbs for automotive applications are usually referenced by the original bulb number like 1157, 3157, etc. If you want to see if they will fit your situation, check at any of the auto parts stores (Autozone, Advance, NAPA, Pep Boys, etc.) to see if they carry them. I know they used to have LED bulbs in stock. If you replace just the bulbs with LEDs you may need a special flasher module that works with both LEDS and incandescent bulbs.
Incandescent style flasher modules typically use a bi-metal strip that heats up when current passes through it. The heat produced by the current flow causes the strip to bend and break the circuit. The strip then cools and completes the circuit.http://auto.howstuffworks.com/turn-signal2.htm
The flasher module that can handle both LEDs and incandescent bulbs is usually all solid state and has a small timer circuit (some are adjustable) that controls the blink rate regardless of the load. Try here for a starting point:http://www.tricoproducts.com/index.cfm?location_id=34
The other type of LED replacement, the full assembly, is described well in this truck lite catalog (right mouse click and choose save-link as, then open with Adobe Acrobat reader):http://www.truck-lite.com/tl/tl/resources/images/en_US/PDF/01LED.pdf
The big deal about LED lights is that they don't draw very much current to produce the same amount of light as an incandescent bulb. Some of the more efficient LED bulbs draw less than 0.1 amp, and even the biggest ones I have seen draw less than 1 amp, and typically 0.5 amp.
If you have any more questions, please let me know. While Natasha and I want the outside of our PD4103 to be as original as possible, we are going to upgrade to LED lights wherever we can, while retaining the original lenses (which we need to find for the rear of the bus).