Lighting

Lighting
A reference list of the original lights in the NHW11 Prius. This may be useful to those considering LED retrofits, as well as those who just want to find the original-style replacements.
About LED retrofits
Many questions arise in the forums about suitable LED replacements for the original lights. This is trickier than it may seem. A suitable replacement should have lumen output comparable to the original, and also emit light in a pattern that works with the original reflector and lens. As of this writing (late 2012), while there are many LED bulbs to be found online with bases that will fit the original sockets, it can still be hard to find one with comparable lumen output to the original light.
For example, the only 31mm dome light replacements I have seen that come near the original 90-some lumens are those built with nine or more LED chips on a flat PC board that extends like wings at the sides of the package. The car's dome light fixture is shaped in a way that might interfere with the fit of such a package.
LED assemblies can try to replicate the omnidirectional light pattern of the original (usually by being studded with small LED chips facing in many directions), or shine a narrower beam out the end (axially, away from the socket), or just in one direction out the side (this design seems to be called 'flank' in the marketplace).
The reflectors and lenses for all of the legal signaling requirements were all designed for truly omnidirectional light sources, and they have to meet legally imposed standards on how much lens area is illuminated at what intensity. These will be the most tricky to retrofit with LEDs in a way that will meet the necessary standards. There is a lot more flexibility to experiment with the interior lighting. The license plate lights might be a borderline case: as long as they light up the plate, probably ok.
More on LED beam patterns
The basic terms describing LEDs for sale (beam angle, axial, omni, flank, etc.) do not always tell you everything needed. For example, a 'flank' LED version of a wedge-base bulb like a 194 is usually built on a single flat circuit board. If the wedge socket is aligned up-and-down, the LED will wind up shining right or left. But what about the license plate lights, where the socket aligns up-and-down but the light needs to shine down? That kind of 'flank' LED is harder to find.
Some shops do seem to sell kits: circuit boards with the proper bases to fit the socket, where you solder on the actual LEDs to shine in whatever direction is needed. That's dedication!
Controlling LEDs
All LEDs need some form of current limiting, either a simple resistor or an active regulator of some kind. Those that are sold as finished, assembled bulb replacements generally include that; otherwise, it has to be provided. Those with regulators will have light output that doesn't vary much with input voltage, which is a good feature for conventional cars where the supply swings around between 12 and 15 volts with engine speed. Active regulation isn't as important on a Prius, where the supply is already electronically regulated to a pretty constant 13.8 volts whenever the car is ready. But it could be surprising if used in a circuit, like the dome or panel lights, that's supposed to be dimmable. An LED with built-in regulation will probably not dim smoothly, but just give constant light down to a point where it flickers out.
LEDs on a turn-signal circuit might not draw enough power to operate the flasher properly, and result in a condition commonly known as 'hyperblinking' (double the normal blink frequency). People tend to solve that problem by adding a load resistor in parallel with the LED in order to draw the amount of power the flasher expects. Needless to say, load resistors negate power savings of going to LED signal bulbs (though the greater longevity of LED could still be an attraction). Instead of adding load resistors, some after-market flasher relays [reference: TapTurn module] can be substituted for the stock flasher relay and are designed to handle (or ignore) the lighter load of LED signal bulbs.
LEDs are naturally polarized, only working with the + and - connected one way. Some packaged assemblies include a diode bridge so they'll work either way. Others don't. For those that don't, it is even more critical to know not only which way the socket lines up but which socket terminal is +, since it won't be possible to turn the LED around if it shines the wrong direction.
I hope that others who do find good LED replacements for any of these bulbs will add the details on this page.
Function Toyota # Common # Best Don'sBulbs match Consumption (watts) Output (lumens) Notes<br />
1 Headlight 90981-13055 HB2 60/55 hb2 60/55 1650/905 <br />
2 Parking lt 99132-12050 947? w5w-5w-12v-w2.1x9.5d 5 50 <br />
3 Front turn 90981-15011 7440a 21 460 <br />
4 Side marker 90981-11020 194 194 3.8 25 <br />
5 Rear turn 90981-15014 or -15011 7440 or 7440A 7440 21 460 1<br />
6 Stop/Tail 90981-11048 7443 7443 21/5 440/35 <br />
7 Reverse 90981-11059 921 921 18 264 <br />
8 License 99132-12050 w5w-5w-12v-w2.1x9.5d 5 50 2<br />
9 Center high stop 99132-12050 w5w-5w-12v-w2.1x9.5d 5 50 3<br />
10 Dome 90981-14011 FESTOON/12V/8W/31MM/11MM 8 ~ 96 <br />
11 Map 90981-12005 SR12V8WMB 8 ~ 96 ? <br />
12 Coin tray 90981-11018 74 1.2 6 ? <br />
13 Trunk 90981-11020 194 194 3.8 25 <br />
14 Center cluster illum. 90010-01039 0.91 ~ 2 ? green cap<br />
15 Combination meter indic. 90010-06019 1.12 <br />


General notes:
Toyota part numbers from toyodiy.com by looking up a 2001 North American/USA model. Others may vary.
Lumens = MSCP × 4π (or about 12.57). As of this writing, Don's database has a lot of errors where a bulb's MSCP rating got entered as lumens, and then the CP figure is shown as 1/12.57 of that. When that happens you can get the correct figures just by multiplying Don's figures by 12.57.
Numbered notes:
1. 7440A for amber signal if lens color is clear
2. Wedge socket aligns up-and-down; light should shine down (off by 90 degrees from a typical 'flank' LED)
3. Though this is the same Toyota p/n as the license lamp, the LED directionality might need to be different (I haven't taken this apart to see which way the sockets align).
Apr 3, 2015