Radiator Fan Relay/LED Indicator

[drewb]

Hi Everyone,

I'm working on installing an LED indicator to tell me when the electric radiator fan is running on my 2012 corolla. I wanted to do this by running 12v wire to the radiator fan relay. The relay is a 4 pin micro relay like the one diagramed here (12 Volt Car Relays Used In Automotive Industry).

Here's my problem: The 3w LED is powered and on when I connect it to pin 2, 3, and 5. However, the radiator fan is not running. 1 is the ground, so I wouldn't expect it to power the LED. According to the diagram I should be able to connect the LED to pin 5 which should be powered when the fan is switched on, right? With ignition on and accessory on pin 5 provides power to the LED even though the fan is not on.

Not sure what to do next.

[thomason2wheels]

Dont know whats happening since I cant see what you are doing but im guessing that led is going to be way too bright especially for driving at night. Might want to think about using a much lower power device. Have you tried using a voltmeter to see if you are getting the fan on off signal to the relay?

[j12piprius]

My thread about a fan light might be helpful.

[samwichse]

First off:

A 3W LED as an indicator lamp? That's the equivalent of a 20-25w incandescent bulb!

Second, if you have one pin on the LED to ground, and the other connected directly to the "go pin," you're putting 12v into your LED. It will be burnt out in short order.

Third, do you have a voltimeter? If so, ground one lead and connect the other side to Pin 5 and tell us what it reads. Silly question, but are you absolutely sure that's the right relay?

[drewb]

Are you saying that you think a 3W LED will be too bright? If so, I don't really care because this probably won't be a permanent addition to my car and I just want to make sure I can see it. It really didn't seem too bright or dull to me in my tests.

I have a resistor for the LED so that it won't burn out.

When you say connect the voltmeter to pin 5 do you mean with the relay plugged in? What would I be looking for it to tell me. I'm sorry, I'm just pretty ignorant when it comes to electrical. I could definitely stand to learn more! Thanks.

[j12piprius]

A 3 watt led would be quite large.

I have 2.5 watt bulbs with 36 leds, and 7 watt bulbs with 108 leds.

Maybe it's .3 watts. Do you have a photo or link to it?

[busypaws]

I did the same LED indicator for the fan many years ago. I used a switch with an LED built in. Then I could drill standard 1/2 inch hole in dash to mount switch. Switch side is not connected to anything it was just cheaper to buy switch with LED built in then an LED indicator.

I was able to find the right pin on the relay. I remember stripping back some of the overwrap on harness and looking at color coded wire (red wire with black strip or something like that). I saw the same wire on the fan that I saw in the relay box so new I had the right pin.