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Thread: Updating with LED rear lights?

  1. #21
    Senior Member Peterv's Avatar
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    They work! It is pin 5 that is ground and all LED's on the outer units work!
    The inner units also work but on the foglights 2-3 led's are out on each. When I bought these lights I told them I'll buy them if all led's work! I'll call them on monday and see if they will send me the 2 fom a 2013 without cost, fingers crossed!
    There is no substitute for cubic inches!

    Jaguar XK 4.2 2006

  2. #22
    Senior Member Peterv's Avatar
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    I read you need 6 load resistors and 2 cheramic resistors to get it to work right but I don't understand why so many and so high watts and Ohm?
    Why would a canbus decoder like this not work, isn't it just a 21w bulb?

    https://www.aliexpress.com/item/2Pcs...d8f54ee2b6205c


    Cut of the connectors and install or.....!?
    There is no substitute for cubic inches!

    Jaguar XK 4.2 2006

  3. #23
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    This is a copy of my tests to establish the parameters that kept my 2007 XK happy when I fitted LED rear brake light units, I used 50W aluminium chassis mount wirewound power resistors that enabled me to bolt them directly onto suitable heatsinks to ensure they remained relatively cool, even during long downhill periods of light braking behind tourists descending the steep incline down to Lynmouth.



    Click image for larger version. 

Name:	50w.jpg 
Views:	56 
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ID:	28121 Jaguar XK Rear Brake Light LED resistor loads at 14.2v

    (14.4v measured at battery terminals, with engine running)



    Original 21w bulb running with 14.2v across it dissipated 28.39w
    Original 21w bulb running with 12.0v across it dissipated 21.84w

    Resistor value Dissipation Result

    12 ohm 16.80w Bulb failure warning on my XK

    10 ohm 20.16w Marginal warnings on my XK

    9.09 ohm (10 ohm with 100 ohm in parallel) 22.18w No Warnings on my XK

    8.9 ohm (3.9 ohm in series with 5 ohm) 22.66w No Warnings on my XK

    8.2 ohm 24.58w No Warnings on my XK

    7.14 ohm (10 ohm with 25 ohm in parallel) 28.24w No Warnings on my XK

    6 ohm 33.60w Overload Warning



    Thus,with the LEDs taking around 6w and the 8.9 ohm load taking 22.66w the combined load was very close to the power taken by the original 21w brake light filament lamp when running with 14.2v across it.

    Highest temperature found whilst scanning across resistors (8.9 ohm) mounted on heatsink at 14.2v

    Start 27 degrees Centigrade
    30 seconds 31 degrees Centigrade
    1 minute 34 degrees Centigrade
    2 minutes 38 degrees Centigrade
    3 minutes 42 degrees Centigrade
    4 minutes 45 degrees Centigrade
    5 minutes 48 degrees Centigrade

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  5. #24
    Senior Member Peterv's Avatar
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    Quote Originally Posted by Godfreyf View Post
    This is a copy of my tests to establish the parameters that kept my 2007 XK happy when I fitted LED rear brake light units, I used 50W aluminium chassis mount wirewound power resistors that enabled me to bolt them directly onto suitable heatsinks to ensure they remained relatively cool, even during long downhill periods of light braking behind tourists descending the steep incline down to Lynmouth.



    Click image for larger version. 

Name:	50w.jpg 
Views:	56 
Size:	32.4 KB 
ID:	28121 Jaguar XK Rear Brake Light LED resistor loads at 14.2v

    (14.4v measured at battery terminals, with engine running)



    Original 21w bulb running with 14.2v across it dissipated 28.39w
    Original 21w bulb running with 12.0v across it dissipated 21.84w

    Resistor value Dissipation Result

    12 ohm 16.80w Bulb failure warning on my XK

    10 ohm 20.16w Marginal warnings on my XK

    9.09 ohm (10 ohm with 100 ohm in parallel) 22.18w No Warnings on my XK

    8.9 ohm (3.9 ohm in series with 5 ohm) 22.66w No Warnings on my XK

    8.2 ohm 24.58w No Warnings on my XK

    7.14 ohm (10 ohm with 25 ohm in parallel) 28.24w No Warnings on my XK

    6 ohm 33.60w Overload Warning



    Thus,with the LEDs taking around 6w and the 8.9 ohm load taking 22.66w the combined load was very close to the power taken by the original 21w brake light filament lamp when running with 14.2v across it.

    Highest temperature found whilst scanning across resistors (8.9 ohm) mounted on heatsink at 14.2v

    Start 27 degrees Centigrade
    30 seconds 31 degrees Centigrade
    1 minute 34 degrees Centigrade
    2 minutes 38 degrees Centigrade
    3 minutes 42 degrees Centigrade
    4 minutes 45 degrees Centigrade
    5 minutes 48 degrees Centigrade
    Do you possible know what resistor you used for the Turn Signal?
    There is no substitute for cubic inches!

    Jaguar XK 4.2 2006

  6. #25
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    From memory!...………….. both original bulbs were 21w, so I would have used the same value of 8.9 ohms for both the Stop and Turn bulbs.

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  8. #26
    Senior Member Peterv's Avatar
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    Got the outer lights working but because of all the different resistor values to use by different owners who have done it I took 2 T10 sockets with 16w bulbs as I figured that would be about the same as OEM bulbs and it works! Made a bulb holder so if/when one breaks I can easily swap them.
    I cut the connector of the 2010 lights and also cut the OEM connector inside the car as I couldn't get the small pins out and change them according the OEM connector. This way I have no connector outside the car and could connect the bulbs at the same time.

    https://imgur.com/a/89x6UGY

    I thought of cutting the inner lights connector open and solder wires to it but would be easier if I could get a hold of the OEM 2010 connectors, would make it easier. In Sweden there are no XK's to salvage from so am hoping someone on here knows of a scrapyard nearby which has a 2010+ car standing and cut those two connectors off and send them to me! I'm afraid if I call a scrapper with a car they won't take the time to find them and send them as it's small money.
    There is no substitute for cubic inches!

    Jaguar XK 4.2 2006

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