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Got a couple of led bulbs for my tail lights. Took the old 1157's out and plugged in the led's. They did not work. Thouhgt it might be the contacts in the sockets so I replaced themhe with the newer spring type. Still wont work.
Took the tail light bucket out and tested it with jumpers direct to the battery. They worked. Mounted them back in the car, still don't work.
Put old bulbs back in and they work fine. What am I missing here?

754997


754998
 

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You need a special flasher, the led bulbs don’t draw enough current to work with a stock flasher. The led flasher has two prongs and a separate ground.
CJ Pony has them, 15 bucks.
 
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You need a special flasher, the led bulbs don’t draw enough current to work.
Shouldn't the parking light work? It is not part of the turn/flasher wiring.
 

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I ran into a similar issue at work replacing several old 6 volt DC sealed beam emergency lights with LED bulbs drove me crazy. In my case the LED bulbs were suppose to work on 6 to 12 volts. They absolutely wouldn't work. I couldn't find anything wrong and some of them meant setting up a ladder to go back up and check. What I found out was that they would only work on 12 volts.

I'm going to go out on a limb and say possibly from the resistance of the wiring it's dropping the voltage just enough so they don't work. Taking the whole tail light assembly out with short jumpers, there isn't the same amount of voltage drop and the LED's work.

Back to my case. When I went back to the supply house with 12 bad LED lamps they didn't believe me until they tried it. At which point we tested all the replacement bulbs they gave me. The first couple were bad and they tested their entire inventory. They had been selling this brand and style for years and never had a problem before. Freaky isn't it?
 

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I like that theory. Voltage drop. I'd be looking VERY close at the ground before anything else.
 

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I like that theory. Voltage drop. I'd be looking VERY close at the ground before anything else.
I thought that too Gypsy, so I ran me a separate ground and they still would not work. If I wiggled the bulb around with the turn signal one would flash. Then I turned on the tail lights and they would only light if I wiggled the bulb around. That made me think the bulb was not making contact with the bucket through the bayonet lugs. Pulled the bulb and cleaned up the lugs and bucket socket and tried again. Same results. Put the 1157 regular bulbs back in and everything worked like it should.
The LED bulbs had been laying on the shelf for over a year. Just thought I try again. Got a lot of extra time on my hands with this virus thing.

yarb
 

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I thought that too Gypsy, so I ran me a separate ground and they still would not work. If I wiggled the bulb around with the turn signal one would flash. Then I turned on the tail lights and they would only light if I wiggled the bulb around. That made me think the bulb was not making contact with the bucket through the bayonet lugs. Pulled the bulb and cleaned up the lugs and bucket socket and tried again. Same results. Put the 1157 regular bulbs back in and everything worked like it should.
The LED bulbs had been laying on the shelf for over a year. Just thought I try again. Got a lot of extra time on my hands with this virus thing.

yarb
Don't assume it's just a ground problem. There's a lot of wire on the supply side.

It's like the old mercury vapor lights. They really didn't burn out, they just kept getting dimmer and dimmer.
 

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Hmmm. I changed over a number of bulbs in my campers to LEDS. Some of them looked just like 1157's but were just a single filament. The rest worked OK but I couldn't get those to work. Same thing, old bulbs fine, new bulbs squat, but they worked right off a battery. So I eventually flipped them over and brought out the soldering iron. I made the solder contact bumps bigger on the LED's and THEN they worked. Except one I'm pretty sure I got too hot, had to toss it.
 
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I used Philips DOT-approved 1157's. Worked great right from the box. That said, I've found that some "Chinese" LED bulb sockets are just a hair smaller than "normal" ones and do not ground properly against the side of the socket. Also, bear in mind that many LED bulbs are "polarity sensitive" and will not work if the polarity is reversed.
 

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Also, bear in mind that many LED bulbs are "polarity sensitive" and will not work if the polarity is reversed.
This! LED’s only light with + volts at the anode and - volts at the cathode. Some bulbs have added circuitry to allow bidirectional operation, but most car LED’s I have seen don’t. Pull the bulbs out of the socket, grab two jumper wires and wire - to the bulb can (socket) and + to a terminal. Try the other terminal. If it lights, great, if it doesn’t, then your bulbs are either broken, assembled wrong, or they could be 1142’s masquerading as 1157’s (1142’s have the same terminal layout but + goes to one terminal and - goes to the other, the socket does nothing).

Very your positives and your negatives on the bulbs themselves and let us know what you find out.
 

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Some LED flashers are not omni-directional, they require power in on the X terminal and power out on the L terminal.

Mechanical flashers will work if the input and output terminals are indexed either way.

Check the indexing on your flasher wiring terminals and swap the wires if the X terminal is not the hot wire.
 

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I've never had good luck with the plug in LED bulbs. Instead, I used United Pacific LED assemblies from Summit racing that replaced the whole tail light lense. I also converted my stock buckets to take a more conventional Dorman socket from O'reilly Auto Parts. My approach is more expensive than using the plug in LED bulbs but it works perfectly without any modifications to the stock flasher.
 

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I have almost all LED bulbs. Probably only a couple regular bulbs in the interior. Haven’t had any problems. Other than the recent failure of the lED taillight panel which died after 10 years

I do have all new wiring and installed two electronic flashers for the turn signals and hazard lights.
 

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You need a special flasher, the led bulbs don’t draw enough current to work with a stock flasher. The led flasher has two prongs and a separate ground.
CJ Pony has them, 15 bucks.
You don't need a special flasher, I just put my LED tail lights right in.

You DO need to make sure you have an impeccably clean ground because they are drawing so much current. I do think there was something else to mine too though that took me a few minutes to figure out.

I bought mine from West Coast Cougar so they were going to have the correct polarity.
 

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You don't need a special flasher, I just put my LED tail lights right in.

You DO need to make sure you have an impeccably clean ground because they are drawing so much current. I do think there was something else to mine too though that took me a few minutes to figure out.

I bought mine from West Coast Cougar so they were going to have the correct polarity.
Same here. Bought from WCC and worked, and still work, perfectly. I had new wiring, so I guess they were clean enough, cuz I didn't have to clean anything.
But replacement LEDs for my brake lights for my Jeep wouldn't work. Same bulb number, same manufacturer, just LED, wouldn't work, so I went back to the regular bulbs. But the Mustang was no problem at all.
 

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You don't need a special flasher, I just put my LED tail lights right in.

You DO need to make sure you have an impeccably clean ground because they are drawing so much current. I do think there was something else to mine too though that took me a few minutes to figure out.

I bought mine from West Coast Cougar so they were going to have the correct polarity.
If the ground was good enough for the old bulbs the Leds should work ok, one of the advantages of Leds is they need less current not more. I had problems with my old lamp sockets, the new ones are not that good either. On my old sockets I was able to clean up the contacts and bend up the tabs to make better connections to the lamps, you just have to make sure you have good connections.
 

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You don't need a special flasher, I just put my LED tail lights right in.

You DO need to make sure you have an impeccably clean ground because they are drawing so much current. I do think there was something else to mine too though that took me a few minutes to figure out.

I bought mine from West Coast Cougar so they were going to have the correct polarity.
The reason LED's are sensitive to connection quality is not that they draw more current as they actually draw less, but rather they are digital instead of analog like a standard incandescent and require a required voltage perimeter to operate. If the voltage threshold is too low they aren't capable of going dim so they go out.
 

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Yeah that's supposed to say drawing so little current, not so much. Obviously LEDs use very little power.
 

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That is the one thing about LED that sucks. You might have an application where a switch works fine with an incandescent bulb but you install an LED and it doesn't work at all. Sometimes you mess with the switch and it will come on, that is due to the switch contacts not being 100% causing a slight voltage drop and not meeting that threshold. Same switch might be fine for years with a standard bulb.
OP, make sure your battery is all the way up as even sitting with the door open and dome light on might drop it enough to be an issue.
 
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