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-   -   LED tail lights stay partically lit (https://www.hotrodders.com/forum/led-tail-lights-stay-partically-lit-118882.html)

cboy 06-25-2007 09:29 PM

LED tail lights stay partically lit
 
I can't quite make sense of this. Last week I put new LED tail lights in my '32 pickup. Tonight, when I shut down the garage lights, I noticed that the tail lights were glowing slightly...through the lens it looks like an LED bulb or two is lit on the top of the array and another bulb or two on the bottom of the array. And it's approximately the same in both the left and right tail lights.

I was too beat to pull the lenses or tackle the problem tonight so I just detached the battery neg. Any ideas what might cause such a thing? I can start putting my tester on the various circuits tomorrow, but if someone has had this happen or has a great idea what the culprit might be I'd appreciate the input before I start tearing things apart.

brian0605 06-25-2007 10:20 PM

Well I doubt it will run the battery down,LED very low draw. I would just leave it in the darkened garage and start pulling fuses from the other circuits one at a time till it goes off. Also is there anything else wired on to that citcuit??? A diode might be in order here. Doc vette what do you think? Brian

docvette 06-26-2007 05:53 PM

Doc here, :pimp:

Check to be sure your not getting a reflection off something else..LED's will do that and look to be lit..

IF they actually are getting power from a source after shut down, Look for a Cap in line with the array, It may not be draining off right away, and holding the LED's on..If that's the case, you'll need a bleeder resistor to siphon off power after shutdown.

BRIAN:

Actually , an LED is a Diode..(Light Emitting Diode) If you counter oppose it with another diode you may end up with a "Crude" Gate..that you can't forward bias to turn it on..(that is a trial and error thing..)

Doc :pimp:

cboy 06-26-2007 07:08 PM

The LED is definitely lit...and not getting a reflection. As soon as I disconnected the battery the lights went off.

What is that "cap" in the line that you mentioned ("Look for a Cap in line with the array")? And where do I go to get a bleeder resistor? Is that something an auto parts store will have or do I have to find it in and electrical supplier?

I should also mention that the LEDs were lit a good 24 hours since the truck was last driven so could that still be the drain off situation you mentioned? That seems like an awfully long time but I know absolutely nothing about electrical gremlins.

Marc Bitler 06-27-2007 10:45 AM

Here's my two cents worth. I was going to put LED taillights in my 40 Chevy and was curious about any problems I might encounter using them. The company who made the taillights first told me that I needed to use either an arm-operated or a button-operated stoplight switch as a pressure-operated stoplight switch would fail. Also, I was told LEDs sometimes will stay lit to a small degree when they are "supposed" to be off. Apparently that happens, but they didn't think it would draw the battery down noticeably. I don't know, I went with regular lights. I would like to have LEDs (they are soooo much brighter) so if there is a fix, I'd surely be interested.

T-bucket23 06-27-2007 11:57 AM

Have you checked with a volt meter to see if there is any power to the socket. If there was a capacitor in the line I would think the LEDs would drain any power off after 24 hours. I would be willing to bet you have a voltage leak somewhere that didnt have enough current to light the regular bulbs but will keep a few leds partially glowing. Check it with a meter. You didnt add any electronic equipment to support the bulbs did you. A place to start would be the turn signal switch, they are mostly pretty cheaply made and could "leak". There are a lot of possibilities, you really need to get the meter out and find out where the voltage is comming from. It is comming from somewhere.If you can make them light without power, you could be a very rich man.

Chet

cboy 06-27-2007 12:20 PM

Quote:

Originally Posted by T-bucket23
Have you checked with a volt meter to see if there is any power to the socket.

I've been trying to troubleshoot this all morning. I get a reading of 15-16 millivolts on the 200m scale of my meter. It is in the brake/turn/flashers wire not the tail light wire. (I'm using an arm type brake switch, not a pressure switch). I also checked it at the turn signals and I'm getting a similar reading on the red/black wire coming in from the brake light switch (attaches at the hazard flasher and the turn signal) Interestingly, when I disconnect the wiring harness for the steering column wires and test the red/black wire coming into the harness from the brake switch I do NOT get a voltage reading at the harness or at the turn signal. But when I couple up the harness again, I get the 15-16 mvolts.

I also tested all the other incoming leads in the wiring harness and did find one with about 15-16 mvolts. This is the white/red wire from the hazard flasher. BTW, I'm getting those readings at the harness and the turn signals with the fuse pulled out for the hazard/stop light circuit. However, the fuse is still in for the turn signal circuit. I'm headed back out to the shop now (mmmmm, nice lunch) and will pull that fuse and see what happens.

As you can guess, I'm pretty confused at this point (which is inevitably the case whenever I deal with the electrical system).

docvette 06-27-2007 03:39 PM

Doc here, :pimp:

An LED can possibly Run for weeks from the drain of an electrolytic Capacitor, provided the Cap was large enough..Like one of those OLD computer power supply caps, 1 MFD @ 100000 WVDC..(The ones that are so popular with Car Stereo Installers now..to keep high current drain stable on "Thump")

A Single LED would last for months on a fully charged cap of that type..a screwdriver to discharge a cap like that will burn/melt the blade like a battery would.

So If you don't have a High power Low Capacitance Cap elsewhere in the car, check at the array circuit boards (If they are accessible) look for an Electrolytic cap on the board, It will say something like : 150 MFD @ 25 WVDC, and have a + and - on it..See if the voltage is there.

Also, do you have a "Ballast" of sorts..on that system to cause enough Draw on the flasher to flash with a mix of incandescent and LED lamps? If so , It may be installed wrong or defective. Check for that.

Doc :pimp:

T-bucket23 06-27-2007 04:10 PM

Quote:

Originally Posted by docvette
Doc here, :pimp:

An LED can possibly Run for weeks from the drain of an electrolytic Capacitor, provided the Cap was large enough..Like one of those OLD computer power supply caps, 1 MFD @ 100000 WVDC..(The ones that are so popular with Car Stereo Installers now..to keep high current drain stable on "Thump")

A Single LED would last for months on a fully charged cap of that type..a screwdriver to discharge a cap like that will burn/melt the blade like a battery would.

So If you don't have a High power Low Capacitance Cap elsewhere in the car, check at the array circuit boards (If they are accessible) look for an Electrolytic cap on the board, It will say something like : 150 MFD @ 25 WVDC, and have a + and - on it..See if the voltage is there.

Also, do you have a "Ballast" of sorts..on that system to cause enough Draw on the flasher to flash with a mix of incandescent and LED lamps? If so , It may be installed wrong or defective. Check for that.

Doc :pimp:

Good Points Doc
Something else to try is with the ignition off flip on the turn signals to one side and see if the other side goes out. If there is a capacitor on teh board that the leds are attached to if you disconnect the plug to the board, theoriginal light plug, the bulb should stay lit with no connection. Also unplug both lights and test with your meter for voltage at the wiring, if it is a real low current leak you may see the voltage go back up to 12 volts when you remove the load. You may also want to take the front bulbs out to test. The problem could be up front also. It takes a lot more current to light an 1157 than an led. Thats for sure.
Also if you disconnect the battery and the light go out you know its not a capacitor in the line. This should be a real simple test. Just remove the negative battery cable.
This will eliminate a lot of possibilities

Lonestar 06-27-2007 04:31 PM

Quote:

Originally Posted by T-bucket23
Good Points Doc
Something else to try is with the ignition off flip on the turn signals to one side and see if the other side goes out. If there is a capacitor on teh board that the leds are attached to if you disconnect the plug to the board, theoriginal light plug, the bulb should stay lit with no connection. Also unplug both lights and test with your meter for voltage at the wiring, if it is a real low current leak you may see the voltage go back up to 12 volts when you remove the load. You may also want to take the front bulbs out to test. The problem could be up front also. It takes a lot more current to light an 1157 than an led. Thats for sure.
Also if you disconnect the battery and the light go out you know its not a capacitor in the line. This should be a real simple test. Just remove the negative battery cable.
This will eliminate a lot of possibilities

He already stated that the LED's went out when he disconnected the battery.

I am with on the theory of a "leak", I wonder what happened when he pulled the turn signal fuse.

If you can identify by pulling fuses which circuit is causing the problem, then it may come down to disconnecting that circuit at various points starting at the tail lights and working your way forward. This should narrow the search down.

Now I am no electrical guru like Doc, but don't they make testers that can "sniff" out shorts and the like?

cboy 06-27-2007 05:54 PM

Shoot. I HATE this. I solved the problem and I have no idea how I did it. I had all kinds of wires and fuses pulled apart trying to track down the stray voltage leak and never really determined for certain (much less fixed) where the problem was coming from. But I finally just decided to put everything back together (one step at a time) and as I did that the LED bulbs never came back on.

I'm still getting a very slight voltage reading at the wiring going to the array but apparently it is not enough to light the bulbs.

BTW, when I pulled the fuses for both the hazard/brake lights and the directional signal lights...I still got the stray voltage reading at the turn signals.

I'll be keeping an eye on it because it might just suddenly come back. Al least this time I think I have some good ideas how to go about searching for the problem.

docvette 06-27-2007 06:02 PM

Doc here, :pimp:

Are you using a Solid state Flasher unit?

Doc :pimp:

T-bucket23 06-27-2007 06:30 PM

Quote:

Originally Posted by cboy
Shoot. I HATE this. I solved the problem and I have no idea how I did it. I had all kinds of wires and fuses pulled apart trying to track down the stray voltage leak and never really determined for certain (much less fixed) where the problem was coming from. But I finally just decided to put everything back together (one step at a time) and as I did that the LED bulbs never came back on.

I'm still getting a very slight voltage reading at the wiring going to the array but apparently it is not enough to light the bulbs.

BTW, when I pulled the fuses for both the hazard/brake lights and the directional signal lights...I still got the stray voltage reading at the turn signals.

I'll be keeping an eye on it because it might just suddenly come back. Al least this time I think I have some good ideas how to go about searching for the problem.

I would be willing to bet it will be back, if it comes back try the disconnecting the turn signal switch.

When push comes to shove it probably isnt even something to worry about as the drain is proably so small it wont effect the battery at all.

I know if it was me I would still want to know why.

cboy 06-27-2007 06:41 PM

2 Attachment(s)
Quote:

Originally Posted by docvette
Are you using a Solid state Flasher unit?

I don't think so (is solid state on a chip board?)...but here are a couple pics. The hazard flasher is on the left and the turn signal unit on the right.

docvette 06-27-2007 07:10 PM

Doc here, :pimp:

Nope, those are standard..

Measure the output side of the flasher with your meter and see if your voltage is there..A Standard flasher is Closed until enough current is drawn to heat up the tungston element, then it opens..

Doc :pimp:


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