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LED rear indicators
- Thread starter terryt
- Start date
Are they the stand alone type bulb? I.E.what would be a single filament bulb if it was a normal incandescent bulb. positive on the bottom pin, earth through the metal body
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It doesn't matter on your old bulb, incandescent bulbs work either way
I wondered how many terminal on the bottom, anyway I checked its just one
The reason your bulbs don't work is because they are wired the wrong way round for your car, its luck of the draw as to which way they wire them
On cars sometimes the bottom pin is positive sometimes its not, never an issue as a filament bulb can work either way round
Obviously an issue though if you want to fit leds
You could buy some more bulbs, but you may have the same issue
Or cut the wires and swap them round (not recommended)
If it was me, I would find the two indicator wires going into the plug on the light cluster, carefully remove the pins and swap the wires over, you can get the pin removal tools for a few pounds or use a couple of small watchmakers screwdrivers
Or if your handy with a soldering iron, remove the head from your led bulb base and swap the wires over, depending what sort of led bulbs they are they come apart quite easily
Thanks for the explanation. Just had a look at the LED bulb and it doesn't look like it can be rewired as the metal cap is soldered to the base which is a printed circuit, rather than just switching and resoldering 2 wires. I'll see what else is available.
Hello terryt,
do you use resistors in parallel connection with LEDS? Are you sure that your LEDS are CANBUS (resistor and coolers on LED?). Pls make a photos of you LEDS. Normal LEDS have cathode (+pin) on bottom pin and anode (-pin) on metal body.
Please try the LEDS on your car battery with one small wire on (- on battery) connected to metal body and than touch with bottom pin to (+) on battery (be carefull with wire!). If no light, broken LEDS.
do you use resistors in parallel connection with LEDS? Are you sure that your LEDS are CANBUS (resistor and coolers on LED?). Pls make a photos of you LEDS. Normal LEDS have cathode (+pin) on bottom pin and anode (-pin) on metal body.
Please try the LEDS on your car battery with one small wire on (- on battery) connected to metal body and than touch with bottom pin to (+) on battery (be carefull with wire!). If no light, broken LEDS.
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These are the LED's I have. I've not added any additional resistors and have tested them on a 12v battery and they do work, positive on the bottom pin, negative on the metal cap.
They don't come on at all fitted to the car so I'm not sure if it is a canbus issue, more likely polarity as dw911 mentioned.
They don't come on at all fitted to the car so I'm not sure if it is a canbus issue, more likely polarity as dw911 mentioned.
Just looking at the bulb in your picture, they can be taken apart quite easily and the polarity swapped over
If you heat the metal base with a soldering iron or a small flame source, you want to get it just hot enough to melt the glue holding the hollow metal body to the leds insert and the two parts will separate once the glue is hot, just pull gently as the two wires are still soldered to the metal body
Unsolder the two wires swap them over, resolder the wires, put a bit of epoxy glue or similar on to the bottom of the led part and push it back into the metal body, your all done
Its quite easy once you done the first one
Here's one I've butchered already, you can see the positive wire in the middle of the cap (piece on the left) and where I've broken it off from the base of where the LED's are. The problem is that there isn't a negative wire I can swap around and resolder. The body cap (negative) is connected to the bottomside of the base where it touches (and is soldered) to the metal ring printed on the base. I'm no electronics engineer though so i could be completely wrong 
No you are correct, it does indeed pick up the negative from the ring around the edge sitting against the metal base
Mine waa different and fitted inside and had two wires, which is why I suggested it, apologies
You could solder two wires to the +&- on the led board and then on the the positive wire in the base (now the negative) and the other lead solder to the inside side of the metal base ,then stick the led to the base with a silicon sealer or similar which will also act as a insulator to keep the outer ring of the board separated from the metal base
Although that's probably only worth doing if you have no luck getting ones with the correct polarity for your mk3
Mine waa different and fitted inside and had two wires, which is why I suggested it, apologies
You could solder two wires to the +&- on the led board and then on the the positive wire in the base (now the negative) and the other lead solder to the inside side of the metal base ,then stick the led to the base with a silicon sealer or similar which will also act as a insulator to keep the outer ring of the board separated from the metal base
Although that's probably only worth doing if you have no luck getting ones with the correct polarity for your mk3
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That could work but I don't want to risk blowing anything on the car. I'll see if there any non polarity PY21W LED's available.
There is no such thing as a non polarity led, just to save you looking
You could try a standard Seat filament bulb, they work either way round
You may be luck and find one that has the negative on the bottom or you may be able to get one of these Chinese sellers to solder you up a couple the other way round
You wouldn't blow anything up, at most you will blow the indicator fuse in the fuse box,That's all
I've found these non polarity bulbs, they don't ship to the UK though and not canbus http://item.mobileweb.ebay.co.uk/viewitem?itemId=251084234877
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