I was going to splice into the #1 and #2 fan relays on my car, but I wanted to wire in an LED so I don't forget they're on. If i have a switch inside the car that controls the relay grond, what do I need to have to make the LED come on with the switch?

 

I use a lighted rocker switch on my car. I am going to be taking some pictures in a few so I'll post them in a while.

Here are the pics,


Here is where I mounted my fan switch,


Here is my dash all lit up and pretty.

 

Hey Zepher, what color did you use for your :hail: dash.. thats really sweet man.

 

Since mine is a B4C, the holes for switches are already there and I don't want to change it.

 

Thanks,
my dash is using the stock lighting

 

92RSB4C,

Firstly, the main thing with LEDs is that most of them dont run on 12 volts; you'll need to add a resistor inline. Someone at Radio Shack MIGHT be able to help you select a proper resistor, or else look at the small selection of 12-volt LEDs they have.

Don't forget that, unlike ordinary light bulbs, the LED won't illuminate if you get the polarity backwards.

I would simply hook up the positive leg of the LED to a source of power that's switched with the ignition key, and the other end to the output of your switch.

The only other problem I see with that is, you're still going to leave the factory fan system in working order, right? So, when the factory computer decides it's time to turn on the fan, your LED would also turn on, which I imagine isn't what you want.

On each of your switches, put a diode inline from the switch's output to the fan relay's input. The diode will let negative signal out of the switch... but not back in. Wire the negative leg of your LED on the SWITCH side of the diode............ turning the switch on will light the LED, but if the computer turns the fan on, the LED won't light, because the diode will block the signal.

(I rarely remember which end of the diode is the cathode and which is the anode, and which does which. Just hook it up, and if the fan won't come on at all, turn the diode around the other way.)

You could also wire the positive leg of the LED to constant power, but then the LED would stay on all night if you left the switch on. If you wire it to ignition power instead, the LED will only be allowed to light up when the key is on.

 

hey guys...i know that i am a little behind here but where do u mount the switch to what wire? someone said something about the wiring it to the ground wire.. but then in the end it didnt make sence... can someone please help me

 

I just wired in a lighted switch to my #1 and #2 fans, so that if my car heats up, I can cool it off.

 

wait... led is a diode... and it wont let the power back in anyway... because it is polorized it will only let power out not back in... so the need for another diode is just a waste isnt it?.. i mean you said that the LED is polorized and can only light if current is going one way... so i dont think u would need the diode

 

If you run to much power through the LED it will burn up.

 

yea thats why u need to put in a resistor... i heard 2.2k is good

 

LOL, I work at Radio Shack :lala:
who wants 25% off