LED light replacement and electrical issue

Hillbilly2, I'm in total agreement with you in regard to it just having to be a short of some sort. It certainly acts like a short. I will let everyone know in the next day or so what I can determine.

At this point there are only two variables;
1. led bulbs in place of the incandesents
2. The LED's may be in backwards (off 180 degrees)

The back of the package does indicate if the led does not light put it in the other way due to specific polarity.

It also indicates guaranteed lighting from 10.5 volts to 15.8volts.

It does appear to have some sort of resistor in line.

did you try hitting them with an ohmeter to see whats going on? there could have been a careless piece of solder than occured when the child laborer in china sneezed, causing a short.

hit it with an ohmeter if it is something like .1-1 ohm something is up. also try making a simplified isolated circuit. like a fuse holder straight to the pos batt terminal, then to a .5 or 1 amp fuse, then your led, then ground. these things will start to isolate where your problem is.

after that i would turn your multimeter to the audible ohmeter function and put one lead on the positive wire in question (say brake light positive) and the other lead on a known good ground (with the brake light disconnected)

if it beeps it means you have a direct short in that circuit. keep on with the above meathod until you can isolate the problem to one component.

now that i think about it- it could be shoddy soldering in one unit causing a short when you switch to all LEDs. or multiple bad soldering jobs. are you sure these are for 12V DC negative ground?

I know the bulbs are correct for the application. I never thought about the poor soldering work by the nine year olds in china. (wow, that is sad)

Any how, that is a great set of suggestions and I will get on that today. Will check back in tonight.

I do have to say that once again, everybody on this site is great! I really do appreciate the help.

A diode will appear as a short when it is forward biased, but will produce a predictable voltage drop, usually on the order of 1 volt. No matter what resistor you put in series, the voltage on the diode will not change (within reason). Only the current changes. The power dissipated by the diode is the voltage drop multiplied by the current. Without a resistor the current will not be limited and the diode will blow. 12 diodes in series will drop (roughly) 12 volts but the current will still be unlimited.

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Originally Posted by JohnC

A diode will appear as a short when it is forward biased, but will produce a predictable voltage drop, usually on the order of 1 volt. No matter what resistor you put in series, the voltage on the diode will not change (within reason). Only the current changes. The power dissipated by the diode is the voltage drop multiplied by the current. Without a resistor the current will not be limited and the diode will blow. 12 diodes in series will drop (roughly) 12 volts but the current will still be unlimited.

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Thats correct, but the diode will only draw the amount of current that it uses. If you were to connect them in series so they all got the proper voltage they would run without a resistor without a problem. About 30 years an old ham told me to think of electricity as water. The voltage is the pressure and the amperage is the flow. A resistor acts as a pressure regulator, in this case the LED acts as a valve. Clear as muddy water? lol

OK people here is the current deal after 11 20 amp fuses.

1. I was able to get four bulbs in and glowing with the running lights on.

2. Here is the current problem however. I was not able to get the brake lights to fire without blowing a fuse (brake circuit)or the turn signals to go without blowing a fuse (turn circuit).

3. What I am left with is the standard incandescent bulb in the brake socket and the LED in the runnning light socket.

4. I did find if the running light ones were in backwards, they blew the fuse. I went one at a time. If you looked carefully at the contacts in socket itself you could figure it out.... or else I just got really lucky... LOL

5. I do know these bulbs are supposed to work in the brake socket. I will check with a guy who carries another brand who has been real helpful to this point with some other 194 bulbs I purchased.


So now it is back to you fine people for some feedback. I think I would be content with the current set up but now it's a challenge to get this worked out. So any help would be appreciated once again.

Jeff

did you take ohmmeter to them yet?

set your multimeter to ohms (the omega symbol) and touch the two contacts, repeat and see if all of the assemblies are identical. this is more than likely your porblem.

Quote:

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Originally Posted by HillBilly2

Thats correct, but the diode will only draw the amount of current that it uses.

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That is not correct. You can drop 12 volts across a starter motor or across a 1 watt lightbulb. the current is radically different, though. Both the starter and the bulb have resistance and the the magnitude is what makes the difference. Diodes do not have resistance as such when forward biased. No current limiting reisitor, no current limit, fried diodes every time.

To put it another way, if you put a single LED across a 1.5 volt battery, it'll get real bright for a very short time period.

for us to help anymore you have to give us some measurements. pull out the multimeter man. . . this has all turned to total theory and guesses.
start measuring and posting.

OK CWillis, I finally got around to using the multimeter....

Here is what I got. by playing around a bit and moving the probes from contact to contact I was able to get consistent readings of 1.6 - 1.8 on both sides. This was only done on the brake / turn light, (middle of three bulbs.).



The regular incandescents work as they should no issues with turn or brake lights signals.

I ran some pig tails off a 12 volt source on the led lights them selves and was able to get them to light off of both sets of contacts.



Still waiting to hear back for the other LED guy I know.

well you werent very specific but here is what i am guessing.

1.6-1.8 is ohms
and you did this by taking out the bulb in question and touching the probes to the light bulb (led unit) and then reversing the polarity of the leads.

if the above is true than you certainly have a bad led. Diodes are supposed to have low resistance in one direction and very high resistance in the other.

This is what makes then act like a valve. Its related to the p-n structure. If you are interested you should google silicone and solid state electronics.

anyways, ill wait for someone smarter to validate this but i would return that unit and get another.

Well I must apologize to CWillis. I totally misunderstood you when you said to take readings on the assemblies. I took that for the sockets and not the lights. It didn't make any sense to me when I was putting the leads on the closed circuit. I went back to the light assembly and took readings. I could only get one reading of around 1.2. I got a similar reading off of a stock 3057 bulb.

So I put the leads on another of the two led bulbs to a 12 volt source and could get two different brightnesses (just like in a 3057, low glow on one filament versus the high glow on the other) except all of the lights go on either high or low depending on what circuit / contacts were energized. I did not get this on the other led bulb, just low current or brightness.

So I am guessing there is where the problem lies. I'll try to return it but it is highly unlikely they'll replace it at this point.

I appreciate all the help, it is time to move on and schedule the glass guy to come out and reset my passenger side long side window so I don't turn the back end into a swamp every time it rains or the snow melts off the truck.

After that it's all new synthetic fluids except for the oil which will remain rotella.

Thanks again everybody for all the help and suggestions it was much appreciated.

When testing diodes including LED's with a multimeter the multimeter does not put out enough voltage to overcome the diodes PN junction. There should be a diode symbol on the selector switch of the multimeter which increases the output voltage at the probes and the display gives you the volt drop accross the diodes PN junction (typically 0.7 volts for a silicon diode and 0.2 volts for a germanium diode). Most meters will display 700 for 0.7 volts in the diode setting and 200 for 0.2 volts. There are other types of diodes which have different volt drops accross the junction. IE selenium diodes which if I remember correctly are 0.3 volts.

A diode if connected accross a battery will act like a dead short. How many of you have connected a CB radio the wrong way and blown the fuse. when you replace the fuse and connect the cb the correct way it works but for some reason a few months or years later for whatever reason you again connect it the wrong way round and switch on you fry the internals. The reason for this is the 'reverse polarity protection diode' which is a sacrificial silicon diode which acts as a short to blow the fuse if the polarity is reversed IE connected the wrong way round. The diode is destroyed and the rig is saved but next time you have a 'senior moment' you are not so lucky as there is no protection because that tiny 1N4001 diode that costs about 2cents wasn't replaced.

There could be 4,5,6 or even 20 amps flowing through an LED and its only using maybe 10 or 20 milliamps to emit light so 4 amps in but 3.999 or 3.998 out etc.

I would check to see if there are current limiting resistors in series with the LEDs and make sure they are the correct resistance. There should be some coloured bands on the resistors unles they're surface mount in which case they'll look like little black bits of plastic with soldered edges with the resistance value printed on them.

If theres no current limiting resistors then it easy enough to buy a 1/2 or 1 watt resistor from radio shack and wire it in series with the LED unit. Try maybe a 5K resistor. If too bright then go to a 7 or 8K or if too dull try a 4 or 3K. they only cost a couple of cents each. Start with a higher value resistor rather than a lower value.

Hope this helps a bit.

Simon.

That really helps a great deal. It is hard to see the diodes, but they are black , plastic like. I'll try to take a closer look to see if I can make anything out on them in regard to size.

Thanks for the info

the diodes are the LEDs themselves. Light Emitting Diode=LED
The other things soldered in are more than likely resistors. they should have a value measured in ohms.

also make sure that when you measure resistance (ohms), make sure you have a DE-Energized circuit. Measuring energized circuits will more than likely damage your meter and at very least give bad measurements.


Chris

Well... I made contact with the other LED light distributor I had purchased some 194 bulbs from and he helped out. I took a flyer on this one and made some assumptions based on my experiences as well as all the great feedback / input I received. I bit the bullet and purchased two bulbs from him. I just finished installing... and they both worked right out of the gate. This brand appears better built and even brighter than the previous ones.

As in the past couple of tries with the original LED's, I had them right next to the light assembly when I pulled out the incandescent bulb. I made sure the contacts were going in the same way as the incandescents and installed and tried seperately as I went. No problems!

So now the rear end is all squared away with new LED's. It is on to the front amber ones.

I'm not sure if this violates websigth policies / procedures ... but if anybody decides to go down this path, I would not hesitate to recommend VLEDS (brand). You can find them on the web or ebay. The best thing aside from the product is that he doesn't screw you on shipping and handling like so many others do.

I would also highly recommend switching out interior maps / domes to led's , they are much brighter and give off better all around light. If you have pairs of map lights you can install one red for night driving and the ohter the bright or super white. I have had the oppertunity to use both and it is a great addition.

Thank You once again for all the help on this one.

After poking around the V-LED websight there is a specific bulb required for the center bulb on older body style chevy's and GMC's. How about that. No wonder I was blowing fuses like they were going out of style. It was also stated if you keep blowing fuses in the brake / turn bulb, then you probably need this special bulb 3157-srck I will try to find out what srck stands for unless somebody out there knows.

Just thought I would throw that out there for future reference.

jeff

SRCK/SACK

The R or A is the color. R for red, A for amber.

The bulbs differ from the standard 3157 in they have one common ground, vs. two ground leads. Probably why you were blowing the fuse. A standard application 3157 bulb can be converted to a SxCK bulb, but isn't worth the trouble, and unsuccessful most of the time. Get the correct bulb. They are unique to the center lamp of 88-99 GM full size trucks, SUV's, and a couple cars. Some Dodge vehicles use them, but I don't know which.

Here is a web site that explains the rear light setup and how to install resistor to make it work...

http://www.plasmaled.com/instructionsled.htm