Jaguar Forums - Jaguar Enthusiasts Forum - LED Project

Introduction
I put this article together after spending approximately $250 for 10 sets of LED bulbs, using trial-n-error trying to find the brightest bulb, as well as a bulb that filled out the reflector and lit up the brake light, tail lamp, and the turn signals. The biggest appeal for me for adding these LEDs is the instant full intensity upon being charged, unlike the old filaments, which slowly light, then dim. Compared to the older bulbs, LEDs are "instant" on, instant off. For a turn signal, the 'instant on' doesn't have any intrinsic value, it just looks "modern", however, on the brake light, a quicker bulb at full intensity gives drivers behind you more time to react, and as people on the internet have stated, at 70mph, that equates to a distance of 14 feet, or something pretty close to that.

On my 2003 XK8, the center brake light above the trunk IS LED based, so adding the LEDs to the tail/brake bulbs matched the quickness of the center, and also helped show how slow the old bulbs really were.

See these video below. The left bulb is an LED, right bulb is OEM filament.

LED PASS only - YouTube

Disclaimer The project was performed on a 2003 XK8. The tail lights and turn signals may be of different design in depth, reflector characteristics, lens color, etc. My opinions made here are what I feel are the best for my particular application. But, take away at least the advantages/disadvantages that I have recognized in each of these bulbs and how they are constructed, but most importantly, how they perform in its intended use. If your turn signal, or brake/tail lamp housings are similar to mine, then I have done all the leg work and experimentation for you, and you now know which bulbs work the best (and are the most affordable).

LED vs Filament Bulbs
There is a common misconception that every LED bulb is brighter than an original filament one. This is very difficult to prove, because a bulb "intensity" is measured from one point near the bulb. One a filament bulb, this is easy, because it doesn't change from one angle to the next, however, and as you can see on the different LED bulb designs, depending on where the concentration of bulbs or diodes are located, the test of the light output can be very different. What I have found in my experimentation, it is not necessarily the 'brightest' bulb, say at the end of the bulb, will not be the best suited for filling out the reflector and therefore, makes it more difficult for other drivers to see you. THAT aspect is the most important, as I discovered the hard way. The more LEDs/diodes on a bulb, the brighter overall the bulb is though, that much is true.

-- 1156 (single pole)/1157 (double pole) are not a DIRECT replacement for the P21W and PY21W. Two problems:
(1) The side pins on the PY21W (Amber turn) are not the same as the 1156. The electronics are identical, but notice the difference in the base in these pics. (OEM on left, 1156 on right)
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The bulb sockets for the front turn signals are VERY sensitive to non-PY21 based bulbs. Just for reference, if you install an 1156 into the front socket, be prepared to keep it in there Til Death do You Part, because removal of that 1156 requires destroying it. I promise you. I've lost two (2) trial bulbs that way. The metal guides that are in the front sockets surround the pins, once you're in, you're in.

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The rear sockets are much easier to 'force' in an 1156 bulb, as you slide the offending pin along plastic, and then resting in the"groove" where the contact is. You can back out the bulb in the same manner w/o damaging the bulb, if you so desire.

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(2) The electrical resistance of an 1156 or 1157 bulb is different than the original filaments. As such, if you use one of these bulbs from your local auto parts store, more than likely, the computer will think the bulb is still "burned out" and give you a message indicator light. The only solution is to put a load resistor on the bulb line to simulate the increased resistance that the P21 bulbs produce. I didn't do any test measurements, but it must be enough of a difference to cause a MIL. To be honest, pay $10-$15 for a new pair of P21 bulbs if you don't go LED as a replacement, the resistor gets hot, you're not saving that much, and it just isn't worth the money you save.

LED Size
Every LED bulb is different. Bulbs on the end, bulbs around the sides, One bulb here, a thousand there - short ones, long ones, running in a circle, running up the side, cluster at the end, some sticking out the sides, clearly, with a clear-as-mud understanding of the performance of these new LEDs on the market, a lot of consumers will buy without knowing exactly what they need, and base their decisions on advertising instead, followed by a incredible disappointment after installing them.

Here is what the original filament bulb measures compared to a couple of LED contenders.

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A reflector is designed based upon the location of that single point burning filament. In order for a good LED bulb to replace this filament bulb, it must generate light pretty much along the entire length of the bulb in order to provide light at the same angle as the original bulb did, but from different locations. Notice the 'angles' in the reflector of the Jag Brake lamp reflector? Anything outside of this reflector can be seen somewhat from the side, but does zilch for the drivers directly behind you.

http://www.superbrightleds.com/produ...%28diag%29.jpg https://www.jaguarforums.com/forum/a...ine=1361895241

Therefore, the short bulbs with clusters of bulbs at the very end do not illuminate the reflector at all. In addition, the length of the bulb has an effect as well. I have tested bulbs that have diodes on the sides, but are not long enough to really use that reflector inside the lamps effectively. Then there have been a few that have really excelled in this department.

Resistors
I mentioned the need to install a load resistor above, and when you replace your old filament bulb with an LED, well all of a sudden, the more efficient LED doesn't draw as much voltage as the previous bulb did, and the computer thinks the filament bulb is broken, resulting in the pass thru of voltage. To combat this, a load resistor takes the place of a filament bulb, and to be honest, I don't know which size works best, but I know I have both 6 ohm and 10 ohm resistors, and both work equally well.

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To install them, you simply put one end of the resistor on the bulb's "hot" wire, and the other goes to the common ground. Which end of the resistor doesn't matter, so you can't screw that up.

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Only bad thing about the resistors is they heat up significantly, and they heat up fast! I can only guesstimate on the temps these things get up to, and I want to say over 150 degrees Fahrenheit or more, which means burn-baby-burn. I got a small blister from trying to move one while it was being charged, and then it also is at a temperature which will melt the plastic, so be careful where you install them. In my case, I used double sided tape, which actually hasn't 'melted' on me, and secured them to metal housings adjacent to the cover plate. See this pic below.

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So far, over 4 weeks of use has resulted in no signs of plastic deformation of the cover plate. For the actual resistor diagram that I used for my rear tail lamp housing w/ turn signal, see this thread here that I completed quite a while ago.

Here is a pic of the original filament bulbs next to the LED (Bulb F). Camera exposure was the same, you can see the difference.

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Here is a pic with the marker lights on - no brake applied. Right LED, Left filament bulb.

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Since I had a lot of the 1156 bulbs left over, I used the really bright SMT (Bulb B below) in the rear fog location. This bulb is not monitored by the car, therefore, no resistor is needed to use this bulb replacement.

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Here is the car with the brake applied and both left and right LEDs (Bulb F) installed.

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Types/Styles of LED Bulbs Tested

So, you want to know which styles are out there, just type in LED 1156 or 1157 on ebay, and you'll come up with pages of LEDs for your automotive needs. It has been written in many locations, that the color of LED you should install, should match the color of the lens. That means if you want a brake bulb in the red lens, you should get RED Led output bulbs. The turn signals, should obviously be AMBER, even though the lenses are clear. So you want to know which ones worked the best for my car? Well, let's look at what I tested out, shall we? In this table, I will summarize the advantages and disadvantages, and then give either an EX, Good, Poor rating for both uses as a Turn Signal or Brake Light Replacement.
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Bulb A - Luxeon

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These were by far the most expensive bulbs that I tested, and one of the first ones that I purchased and installed. Light output on these were among the highest, but unfortunately, it consisted of one single LED bulb, and that bulb overheated within 15 seconds at full intensity, resulting in auto-dimming to protect itself. It also did absolutely nothing in the reflector in either the turn signal location or brake lamps.

Turn Signal: Poor Brake: Poor

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Bulb B - SMT Sides & 3 Front

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By far, this bulb is one the most useful design. It has a lot of side lighting, I would say about 25% more than the 3 SMTs on the end. Fills out the reflector very well, but needs more LEDs on the end, and a little longer to make it a perfect all around performer.

Turn Signal: Excellent Brake: Good
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Bulb C - 3 SMTs Front

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This bulb doesn't really have a place anywhere, as all of the light output is at the end, and nothing gets to the reflector. Similar in performance as Bulb A, but at least this one didn't overheat when in use.

Turn Signal: Poor Brake: Poor
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Bulb D - SMT Sides, 5 LEDs Front

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This was the best design that I saw, lots of SMTs on the sides, fairly long enough, and the 5 LEDs in front made it eyecatching to drivers. Only problem was that it did not work in my tail/brake lamp socket?? Both sides did this, and strangely, it did work in another socket (the dedicated indicator tail lamp) which I didn't really need. As such, I gave it good grades for both application, but be warned, it may not work.

Turn Signal: Excellent Brake: Good
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Bulb E - Small SMT Sides and Front

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These bulbs were the priciest, due to the newest technology in LEDs I presume, at $40 + S&H when I bought them a couple months ago. They are equal in performance as Bulb B, but waaaay more expensive.

Turn Signal: Excellent Brake: Good
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Bulb F - 18 LED

https://www.jaguarforums.com/forum/a...ine=1361895241 Click for Larger Pic

I liked the design of these bulbs. The flat diodes on the sides really lit up the reflectors, and were much longer than all of the other bulbs. As such, the entire reflector was illuminated, and with the 3 LEDs on the front, it looked almost equal in output all round. This bulb worked well in all applications.

Turn Signal: Excellent Brake: Excellent
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Bulb G - 20 LED w/ Bumps

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What looks a lot like Bulb F above, it is clearly not. At first glance, the bulb just adds two additional LEDs on the front, and it just as long as Bulb F, so why the poor ratings? This bulb doesn't have flat diodes on the sides; they're bumpy and the 'diameter' of the bulb now exceeds the maximum that will fit in either the turn, brake or tail lamp indicator bulbs. Booo on this manufacturer for duping me!

Turn Signal: Poor Brake: Poor
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Bulb H - 36 LEDs

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This bulb design was one of the first ones to be released, put several circular rows of LEDs along the length of the bulb, add some on the end, and cal it good. The light output was pretty good, only problem here was the length of the bulb. It wasn't long enough to illuminate the rear of the reflector, therefore, did not score well with me.

Turn Signal: Untested Brake: Poor
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Bulb I - 24 LEDs

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Similar to the design of Bulb H above, but this time, most of the LEDs are placed on the end, and some radially firing ones were supposed to fill out the reflector. It failed, miserably.

Turn Signal: Poor Brake: Poor
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Bulb J - 45 LEDs

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This one is similar to Bulb H, but looks to have an additional row of radially installed LEDs, which should help with the reflector performance. It is shown to be 50mm long, which is almost as long as Bulb F. This turned out to be pretty good, and would be my second choice for the turn signals. Brakes were all-right as well.

Turn Signal: Excellent Brake: Good

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Bulb K - Five (5) 5W Cree LEDs w/ a projector-type lens on the end.

https://www.jaguarforums.com/forum/a...ine=1361895241 Click for Larger Pic

This one is a new LED design, and has performed VERY well in brake and turn signal applications. It doesn't look as 'circuit-boardish' through the clear tail lamp lens, so that's a plus. It is one of the most, if not the most expensive bulb, however. $47 for a pair of bulbs containing built-in resistors. I've updated my rear bulbs in the XK8 with these for brake and turns, and they are installed in both my front and rear turns in the XJ8.

Turn Signal: Excellent Brake: Excellent

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Here is a video of both LEDs installed. Now, it matches the 3rd brake light exactly!

LEDs both sides - YouTube

ALTERNATIVES

I even tried a bulb manufactured by Philips that claimed that it would illuminate 50% faster than the regular filament bulb.

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Unless I am mistaken, this video shows the same delay that the original bulb had. It failed my test.

PhillipsUltraPASS - YouTube

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