Calling all electrical experts

[JLAWS]

Hi guys I upgraded my tail light on my Lexus Ls430 to 2005 tail lights which has a cleaner clear strip turn signal vs the old ugly orange strip. Unfortunately those are LED lights and I get a "tail lamp failure" message because it draws such a low current and thinks the light is out. I tried load resistors but they get pretty hot and draw too much power and the lights are dim. The only remedy so far is to wire on some #3157 light socket and bulbs so it draws enough current. It looks silly exposed and the lights get pretty hot. Is there a way to immitate a 3157 bulb wattage using something else. Maybe the dealer can get rid of the message?

The socket has 3 wires, (2 positive and one ground) any help is appreciated, thanks

[JimD]

Two things to check:

1: Resistance value of your load resistors. You are trying to simulate an incandescent bulb that has a very low resistance (

2: Wattage rating. Are you using at least 100W resistors and have them physically attached to the body for heat sinking?

Putting a 3157 bulb in parallel may look silly but unless you can come close to the same resistance with high wattage resistors, the bulb is your solution. I will decline the expert in the title.

[Oldgamer]

If you connected resistors correctly I think the lights were not dim, cause to make them dim resistors should drain so much power that they can be burned in fraction of second. Try to connect 2 bulbs. One bulb connect to the first positive wire and the ground wire, and the second bulb connect to the second positive wire and the same ground wire (you saing it has 2 positive and one ground). Try to use as small bulbs as possible, have a power just enough to avoid a message. Place them somewhere where it's ok if they got hot.

[Scotty]

Look at this thread it may be helpful.

http://www.dieseltruckresource.com/showthread/t-48628.html

I especially liked this:

superbrightled.com sells 6 ohm x 50 w resistors that are encased in an aluminum sheath with cooling fins. They provide a 2 amp dummy load.

I could not find those resistors on the site however...

[JLAWS]

Thanks guys I really appreciate the feed back even though I don't own my Caddy anymore. As always a bunch of cool guys willing to help out.

[jhall]

JLAW,

You'll want to keep the watt dissipation on the resistors to a relatively low value to avoid heat problems - as well as keep the cost down.

See attached drawing. Assuming that a 2 amp load is needed, you can use four 25 ohm resistors in parallel to the light bar, the max wattage per resistor is about 6 watts- cool enough to touch. Cost for these is about $1.90 each from Newark Electronics part # 01F7487 - Ohmite resistor number 20J25R (10 watts max).

As an alternate, you can use eight 01F7494 50 ohm resistors and will only need a 5 watt rating per resistor, though these are typically only available in a 10 watt rating. Cost is also $1.90.

You may need to double the use this type of circuit - one group for the running lamps and one group the brake lamps to avoid the "blown bulb" message.

Getting the correct resistor value and wattage is a bit of a dance since there are specific standard values that are manufactured and these values have a limited range of watt ratings.

Hope this helps. Good luck

LED_bar.doc

[navion]

JLAWS,

Just remember, whatever you add to bring the resistance up to equal the 3157 bulb will put out the heat equivalent of the 3157. That heat will have to go somewhere. Be careful. Don't build a "Fire Starter" in your trunk.

As someone once said, "Watts is Watts".

If the car's computer could be reprogrammed or the function just turned off would be best.

LED's are great. Hopefully you can find an easy fix.

Britt

[jhall]

Yeah,

I'd agree. If there's a way to turn off the lamp monitor, this would be the best route.

[CaddyChris]

JHALL,

I think you definately offer a viable solution.

Chris