VW T4 Forum - VW T5 Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
1,318 Posts
Discussion Starter #1
Hi.

I have purchased LED type door lock pins.
I want to wire them up, so that when my ignition is switched off they come on (I.E. pretend security led's).

I am told the best way is to feed one side of the LED to permanent live feed - then wire the other side to a live ignition feed, that goes to ground(negative) when the ingniton is turned off.

I plan on doing this in the next few weeks, and i do have a meg-meter available to search for the required wire.


My question to you electical guru's :-

Does this sound correct ?
Is this the best way to go aobut this job ?
Do you know which wire at the back of the ignition switch is live when on, and negative when off ?

Regards

Brian.
 

·
Registered
Joined
·
1,656 Posts
That will work, but it's not strictly a negative.
Although an LED wouldn't allow much current to pass through it and also depends which way it's biased, I wouldn't really fit a diode between those two circuits. Especially if those wires used carry any data lines. Also If the LED did burn out or go s/c your switched live would be live all the time and the wires for the LED will melt.

Use a relay and wire the LED Anode (+) to 87a on the relay, with a perm live connected to 30 on the relay, ground on 85 and switched live on 86. Ground the LED as normal. The relay will be normally closed when power is off, when you turn the key the relay will energise and switch the LED's off.

If the LED's don't have any resistors fitted, fit one as they may burn out, it's not the voltage you are trying to limit with a resistor it's the current, LED's will take as much as they can and burn out.

There are other ways with transistors etc, but a relay is a cheap elegant safe solution.
 
1 - 5 of 5 Posts
Top