LED tail lights, etc. strange behavior.

[Rocketman3]

This is just an FYI…

On my 23 year old rig a lot of the lights were dim- running lights - tail lights,etc.  So I have replaced them with LED Lights. Over the last couple of years, I have replaced all the lower running lights and tail lights (turn, brake, running).  I like the LED’s from M4 products- the 1157 bulb is really bright. 
 

However, all of a sudden the turn lights were not working correctly when the headlights were on.

Each side of my taillights are two (GM?) taillights (one of them is upside down) - so I have two bulbs per side. 
 

I figured out that with one or two regular 1157 bulb - it was working correctly but with two LED bulbs - it was wacko.  I think the flasher circuit just needs more draw than all LED will provide.

[Dennis H]

Simply wire and 'extra' 1157 bulb in the circuit. Hide it somewhere so it doesn't show and you're good to go. Only one bulb should be sufficient...Dennis

[Gerry f]

Michael,

Since you said that the light's were getting dim,  it sounds like you may have a bad ground somewhere in the light circuits.  I have converted all of my exterior lights to LED's.  Didn't have any issues until I changed the front turn signals to LED's. They did not want to flash.  I just added a load resistor to the both the left and right rear turn signal lines.  I put the resistors on at the rear because it was easier to get to and more room to work.  You can find the LED load resistors on Amazon.  Very cheap.  Just make sure that they don't touch anything the might melt as they can get hot.  As you can see by IMG-4515 they do get HOT!  That fixed everything.  You are correct that the LED's draw so little current that the flasher unit does not want to work correctly.  But the load resistor on both the right and left turn signal lines will fix that.

Good Luck,

Gerry Faulkner

2007 Executive Sandia IV 

[Just Jim]

I know this is an older thread, but I'm curious about the resistors.  I installed LED tail light fixtures and they came wired with 100w resistors.  I turned on the parking lights for about 30 minutes and they stayed cool.  I thought about screwing them to the fiberglass, but had seen before that they can get hot, so for now I zip tied them to a steel frame section.  What does it take for them to get hot?  Leave them on for hours?  Stop and go traffic (constantly applied brakes)?  I am thinking of using a metal hose clamp and attaching them to the steel frame.  Does that sound like a solution?

[Gerry f]

Jim,

The load resistors are NOT connected to the parking lights.  They should be connected to the turn signal bulb wire and the other side to ground.  They provide the additional load that the flasher needs to operate.  The LED's take so little current that the flasher may not work properly without the additional load that the resistor provides.  Again, the load resistor is NOT for the parking lights but for the turn signal bulbs (LEDs).  One of the right and one for the left signal.

I would NOT attach them to anything thing that could be damaged from the heat of the resistors.  Attaching them to a steel frame would probably be okay as long as the metal hose clamps will not move and accidently short out the voltage side of the resistor to ground.  That would cause the turn signal fuse to blow.

Gerry Faulkner

2007 Monaco Executive

[Just Jim]

Thanks Gerry,

The resisters were built into the new housing/LEDs that I bought... nothing to install or wire up other than mounting them somewhere.  I also had a suggestion of using a steel zip tie to mount them.  The lights are all in one, parking lights, turn signal and brake.  The only one not included is the back up light and its a different socket.  So, that is why I was wondering about what actually causes the heat to be generated as just the parking lights didn't do anything.  The brakes and turn signals work fine, but can't see them causing a lot of heat unless you were stuck in traffic and on the brakes a lot.