I have replaced my factor tail lights 1157 with LEDs.
besides the turn signals taking a bit longer to come on cuz of the less voltage now required I have noticed that they are very dimly light when the key is turned on and light switch off. left and right sides are lit evenly.

is this a ground problem? or is this expected when putting LEDs in older vehicles?

 

We have LEDs in a truck at work. They do the same thing when the truck is running. They are very very dim. I think its because they take so little power to work.

-Matt

 

This is strange. There must be a high resistence path to the lamps even with the headlight switch turned off. You could speed up the turn signal by putting the old bulb across the tail lamp. Just hide it. The current flow will then be greater. That would also stop the dim while key on condition.

 

I would rather not use an in-line bulb. I am running a 4" crank pulley so I am trying to save some power at idle without having to by a larger rated altenator. I have already made an aluminum altn pulley reduced by 5/8" in dia but is still not enough.

 

Use an astable multivibrator circuit, built to pulse to whatever interval you would like, to drive relays for the lights. Do a search for 555 timers. There is lots of stuff on the web and you need very little knowledge of electronics to build yourself. The end result will get you the desired interval regardless of the resistance provided by the bulbs and/or LEDs.

It's a fun project, try it.

 

why not go to the parts store and buy an electronic flasher? they are about 7 bucks at auto zone here.

 

thanks for the input. happy new yr! I've been away.

damonlan, I like the 555 timer idea. it looks very usefull and this setup could be fun and easy to make. but I don't really have the time to further educate my skills on it.
but if I do try it I think this is about the easiest breakdown for it. http://www.technologystudent.com/elec1/5555.htm
is this the right direction?

OFTR, I didn't think the electronic flashers were that cheap. will it replace any old style thermal flasher? I think I'll give my autozone a call for price.

 

Hmmm...
I have LED replacements for my 3157 bulbs, but have similar anomalies. Flashers act as if there is no load(in fact, like no bulb at all), and the stock Hi-mount stop light bar(an LED itself) is always partially energized when I install the LED replacements. Very weird.
My '98 Explorer already has an electronic flasher, but the system seems to sense a "failure". This car has a shared relay center module.
I'm not sure how to go about solving this problem. AI'd appreciate any suggestions?

 

That is what you are looking for. Remember, the blinking LED in the diagram is only one LED, not an array. You will need to find out the current draw of you array to figure out how many amps will be going through the final transister. The best bet here is just to use an NPN transister rated for about 10 to 15 amps. They will be available for about 2 to 3 dollars at you local electronics store (probably NOT Radio Shack). Then you won't have to worry about figuring the amperage, the 10 Amp rating will be way more than the array will draw.

On second thought, your tail light array probably already comes with the resistors manufactured in series with the LED's. In that case, replace the 270 Ohm resistor with a 12 Volt rated relay, (the coil connections of the relay). The circuit in that diagram can be run on 12 volts instead of 9 volts because the rating on most 555's is up to 15 volts I believe. Then, replace the blinking LED in the diagram with any diode rated for 2 amps or better. Make sure the diode's anode (striped side) is connected to the ground side of the relay coil (The sripe orientated up in the diagram). This coil is necessary to rerout inductive cick away from the transistor junction. Then, just use the switch part of the relay to make and break the power to the LED array. Simple.
The only thing that will change with this configuration from the original diagram is that the array will blink on when they used to blink off, and they will blink off when they used to blink on.

Third thought, eliminate the relay. Just make sure the final transistor is rated for 10 to 15 Amps. Then connect the hot side of your array to +12V and the ground side of your array to the collector of the transistor (the angled leg without an arrow). This is the easiest way yet.

 

Also included in the third thought. Don't need the 270 Ohm resistor or the diode or LED any more. Just simply using the transistor as a switch actuated by the pulse of the 555 timer.

 

denim-
It is acting like there is no load because there is practically no load. The LED's use about 1/10 of the current per Lumen output. Because the relay needs a fair amount of current to make it operate (by heating a wire and increasing resistance) this may never accur. At those low currents, the wire will probably be able to sink more heat than is generated by the small amount of current going through it. This will result in very slow blinking or no blinking at all. Must be a seperate relay for the flasher LED replacements sold somewhere.

 

thanks damon. I think I'm getting it but it's not something I do much of. yeah, the working volts on the timer are up to 15 volts and I think as low as 3.
so the NPN would be wired as a common emiter circuit?
collector to ground and base to 12 volts.