led lighting problem

I'm in the process of swapping as many of my lights for leds as I possibly can..I have done the whole dash,3rd brake light and the rear signals (hijet) have some more leds coming but I have an odd problem..I replaced the rear combination brake tail-lights with red 24 led dual function bulbs..worked perfectly for 2 days then my brake lights wouldn't turn off??...after checking everything including the brake switch,I have traced it down to the right rear....if I put a regular dual filiment bulb in that socket the brake lights work fine..with any led dual bulb the brake lights will not go off...conclusion is that there is enough juice from the taillight wiring leaking into the brake circuit to illuminate all my brake lights,but with a regular bulb in the socket,there is sufficient resistance to negate the effect...checked all the wiring and can not find any dodgy connections or crossed wiring......any thoughts ?? I picked a bad week to lend my electrical tester to a dude 70 miles away:frustration:

 

The turn signals have been fine actually other than they flash quicker..haven'y done the fronts yet though and with them in the circuit resistance my then become a problem as you say.....my buddy next door converted his Volvo 18 wheeler over to led a few months back and says the reduced draw on the alternator is a huge bonus...he showed me some stats on the extra benifits of led for brake lights and the quicker lighting of the leds when you hit the brakes actually gives the person following you an extra 30-40 ft of reaction time

 

interesting, i was thinking about this myself for my truck as i have done a few led's in my house.

fupa, i remember we tried doing this on a mid 80's/early 90's vw jetta and the same result happened on the 3rd brake light. As im into early vw rabbits from what i understand there are resistance issues and cant be done on them. You are probably having the same issue.

Now i have to go all around my sambar and see what bulbs i have to change over lol

 

I'm sure it is a crossed wire somewhere as it didn't misbehave for the first few days

 

finally got around to checking it...seems there are .45 volts coming through the brake light circuit (on the drivers side only )when brakes aren't on....doesn't bother the regular bulbs but is enough to permanently light all the brake lights when a LED is put in..

 

Sounds like somthing a Diode may cure?

However, it is weird that the LEDs themselves forward bias with 0.45v being that they are just diodes that consquently make light.

 

I thought that was odd as well...a diode should only allow current to flow in 1 direction which is why they always have a pos and a neg side? or am I wrong on that?

 

Diodes also drop voltage when fwd biased. Typically 0.7v is the drop and the potential diff needed to open. so the diode may just block the 0.45v your seeing in the "off" state. When you turn on your lights, the diode will then fwd bias and consume its 0.7v pay for its job. y will need to know the amp draw to determine what power diode u need. 0.7v times current equals how much power in the form of heat it will consume for its job. I bet diodes can be found in lower voltage flavors these days too.

EDIT: Im making the asumption that someone else (original or aftermarket circuit designers) put a current limiting resistor in there some place. and all you need to do is block a little voltage. Perhaps a bad asumption. Best thing to do is look at post #15 b4 doing anything.

 

Wonder if this bad boy would do the job 1A continuous, 30A surge. Have to hang an amp meter on your tail light to see what the deal is.

http://www.radioshack.com/product/index.jsp?productId=2036268&CAWELAID=107597561

 

or get the upgrade for 50cents more! 3Amp continuous 200amp surge. 200v reverse bias

http://www.radioshack.com/product/index.jsp?productId=2062579

This one looks like it may steal (up to) 1.1v If you really want power efficiency, this may not be for you. it will draw up to 3watts max (beyond that think of it as a "fuse" =P )
http://www.datasheetcatalog.org/datasheet/WINGS/1N5406.pdf

 

good article on this stuff... I jumped down to "USING LEDs"
http://www.gizmology.net/LEDs.htm

 

please forgive my constant hammering on this thread... But this is also helpful info...

Summary: Changing to LED bulbs drops the current useage and freaks out your flasher module in one of two ways: "1. Most commonly it will flash too fast, about 2.5 cycles/second instead of the 1 cycle/sec that you're used to. This can be annoying for some people. 2. The lights might not blink at all, but just stay on constantly. " --from site below SOLUTION: get a different flasher module or load the system with more current. (i kinda like my idea of the diode though, hehehe, but it probably wont work if the flasher is going wonky).

http://www.bugmanweb.com/gsxr/flasher.html

 

I agree.it is helpful... thanks for the info o8k...... my led turn signal swap was no problem ..I had already assumed they would flash more rapidly and they do slightly, but it isn't anything I can't live with.I still need to isolate that voltage leak in the drivers side taillight...it seems to be the cause of the brake lights coming on. After reading the gizmodo article I think I'm wanting UV leds in the dash to make everything glow I'm like a chimp when it comes to shiney stuff....ooook

 

Maybe you have "Zener Diodes" some how, which allow current in both directions at preset levels. Don't know why you would, I only saw those installed on a couple of things in the military....

 

Nope not zenners...I have those in my Saeco automatica coffee machine..they kind of flicker like a candle

 

Well I had some time to tackle this again ....the simplest explanation as usual is the answer..the dual contacts on the base of the bulb...one is slightly miss aligned and making just enough contact with the brake circuit to send power to the brake light when the taillights were on...slight surgery on the bulb base contacts and the problem is solved ....I'm 80% led now..even changed the halogen H3 foglights to h3 smd leds ($6.95 inlcuding shipping for the pair) I've got replacements for the license plate bulb and interior lights on the way..headlights will be the only non LED on the truck ...once they are all in I'll post the amperage draw..then swap them all back and check the difference....My hope is to increase voltage to the coil at all rpms(reduce slight voltage irregularity would be a better way to put it) with the reduced power requirements of the LEDS..I already seem to have a smoother idle..

 

You should post some pics of the process, I know I'd be interested!

 

I second the motion...

I'd also like any more info you can give. I'd like to convert my trucks lighting.

z

 

Here is your quick headlight replacement (or aux lights and you wont need headlights anymore): 1000 lumen LED work lights

However, not a good "on-road" option due to brightness.

Here's a picture of a pair custom mounted:


And here's a quick night video showing their effectiveness in snowy conditions: Mini Truck LED Work Lights on Blower Truck

 

ya those suckers are bright...I doubt I could get away with using em for headlights..I may get a set for fogs tho those are sweet...I will post the results and get some pictures as soon as possible

 

Can't help myself...

I just gotta ask... whats the supposed problem with the negative battery cable terminal touching body or frame? Once you've removed the terminal from the battery... you have broken the circuit... just sayin...

z

 

Z not sure how I missed this post...but not sure I understand the question??

 

lol looks like the post I was replying to has been removed (boy do I look crazy or what?).

z

 

They make a flasher for led lights they are called electronic flashers I got mine on ebay for about 15 bucks haven't put everything together to see if they all work together but I put one on the front and turned on the turn signal to find the correct wire for the back turn signal and it worked fine. I did notice that if you don't have any lights hooked up that the electronic flasher will not do anything. As soon as I hooked one light up it went to clicking and worked like it should. Kinda weird but whatever they work!

 

if you will disconnect "-" on running enging, say goodbye to your electronic ignition block, or maybe not LOL