Fog Light Switch [LED Light]

[Nathanb]

Should have been clearer Nope didn't just try it in the multimeter.

I tried the LED in the actual switch and it doesn't work, old bulb does now work so switch is good.
I also tried the LED in my setup when I had a wire coming direct from the copper strip and also the spade connection, with LED connected in the middle. Again LED didn't work but old bulb does.

What threw me off at first and made me think that the LED was working is that when I attach it to the multimeter [tried it on two different multimeters] the LED lights up, but as I said it's very very dim. So at first I thought perhaps that's just how it should be. It's very odd that the multimeter is giving it a low voltage and makes it light up whereas when in situation in the actual switch it doesn't light up at all.

[MidLifeCrisis]

I still don't get how you tested/lit an LED using a multimeter??

[Nathanb]

I don't get it either!!!!

When I tested the LED dash upgrade lights with the multimeter on the Ohms resistance audible setting, as expected I get an audible buzz.
When I test the LED Fog Light Switch upgrade with the multimeter on the Ohms resistance audible setting, I get NO audible buzz but the LED itself lights up very dimly.

I'm going to have to take a photo aren't I to prove that I'm not going mad!!!

[Oldiebut goodie]

You aren't going mad.
It does work! Not on all leds but definitely does on some - try it! Test using diode setting which is better than ohms. No good on IR ones unless you view with a camera.

[MidLifeCrisis]

Ok - I understand now - so have you actually tried connecting the led to a 12v battery - as it seems like it might be working fine?
That would also confirm which is the positive and negative connection - and whether that matches up with the polarity at the fog light switch.

[CovKid]

Only if its a 12v LED. Most aren't and use a resistor in the circuit to step it down. If you put 12v straight across an LED it'll go with a nice pop.

[CJH]

I did that with a COB LED out of a cheap tail light bulb (that had come apart) - burned like the sun for a few seconds then went pop.

[CovKid]

Big Clive has some interesting observations on large LEDs - verified on my own bench with a variable power supply:

https://www.youtube.com/watch?v=_wR_mFWeI6Y" onclick="window.open(this.href);return false;

Unfortunately I'm finding similar problems with smaller LED packages which is why I tend to wire them up myself using known good components. I think if it were me I'd see what voltage is available at the original light then using a simple LED calculator ( http://led.linear1.org/1led.wiz" onclick="window.open(this.href);return false; ), fit a suitable resistor. All maplins LEDs have the spec needed to calculate the resistor altghough probably better to use a low brightness LED or increase the resistor value so it doesn't actually blind you. Simple enough once you've done a few and better than the cheap Chinese stuff. Replaced all my dash lights using this approach - at a fraction of the cost.

I've not taken the fog light switch apart as mine works, but I suspect you'll find a resistor inside it. That could have blown causing an open circuit I suppose. You can ofcourse fit the same to the headlight switch if you make a small hole for it although better to utilise an unused LED slot in the centre of the dash - say a yellow one to show your lights are left on. Once you get into it, you can light up all the bits that VW missed. Armed with a stack of LEDs and resistors you can spend a happy evening rethinking the display including micro LEDs for fuel and temp gauge.