LED to indicated fan ON/OFF

[CDeeZ]

Hey everybody,

So I was killing time in radioshack the other day and I was browsing the LEDs and I got an idea...... I'd like to put an LED in my dash that lights up when my Efan is commanded on by the PCM...

I guess an LED really isn't that complicated, but I was reading up on it on the internet and it is definitely not as simple as a conventional incandescent bulb!

My question is this: how do I know if the LED i selected will work properly in my Efan circuit?? I could just wire it up and be ready with the fire extinguisher LOL.

Specs: Forward Voltage: 12.0 TYP, 16.0 MAX

Forward Current: 15mA TYP, 25mA MAX

The LED also has a built in 680 ohmm resistor........

Will this LED work okay in my Efan circuit?????? I've been playing around with it on a spare 12v battery in my garage and it seems good to go that way.....

Thoughts?

[PJG1173]

I did this with regular mini bulbs. I tied into the power actually going to the fan after the relay vise looking for when the pcm commanded the fan on. that way I can see when and verify the relay controlling the fan is activated. I have been looking at using LED's vs regular bulbs in my setup because when the fan spins even with out it being on the bulbs will light up and get brighter the faster I drive. I am hoping the LED's don't do that, any how I was planning on wiring them in the same way but with a diode in series to get rid of the small voltage signal the fans produce while spinning without power applied.

[gregs78cam]

...

Will this LED work okay in my Efan circuit?????? I've been playing around with it on a spare 12v battery in my garage and it seems good to go that way.....

Thoughts?

Sounds like it should work fine.

[RobertISaar]

that LED will be fine. with the current it needs(minimal), you can either tie it into the switched ground for the control portion of the relay or on the load switched side of the relay and it will work fine.

if you want a mspaint diagram, let me know.

[91ss]

If you wire to the load side of the fan, you may see it light up some at highway speeds as it may turn fan fast enough to generate some electricity.

[PJG1173]

If you wire to the load side of the fan, you may see it light up some at highway speeds as it may turn fan fast enough to generate some electricity.

there's no may about it. it does, but it is so dim its hardly noticeable

[EagleMark]

OK, I'm all for cool stuff, but what is the purpose or need of this LED indicator? I think I'd rather have the opisite! If fan did not turn on when supposed too then Light on? Assume all is well until not... except for the Nitrous Armed light!

[RobertISaar]

depending on the application.....

a lot of clusters got "check guages" or even a direct "engine hot" light that came on when above a specific temp... it's always way too high from the factory and requires changing resistors on the backside of the instrument cluster to "tune" it to the temp of your liking.

[Six_Shooter]

Specs: Forward Voltage: 12.0 TYP, 16.0 MAX

Forward Current: 15mA TYP, 25mA MAX

The LED also has a built in 680 ohmm resistor........

It's a 12V LED (due to the 680 ohm resistor to limit current), so treat it just like a conventional bulb, with the only exception being that it is polarity sensitive, so you need to make sure you have the polarity correct or it won't work, and likely damage it.

To use an LED like this on the fan side of the relay, without the feedback voltage created by the fan spinning due to airflow through the fan at speed, you would need to split the fan wire between the relay and the fan, placing the stripe towards the fan (electrically speaking), and connect the LED on the relay side of the diode. You will need to use a rather large diode, or several paired up in parallel, to live through the current that the fan demands.

If you wanted to have the fan turn on only when the fan is both commanded on by the ECM and the relay activates, you can connect the anode (positive connection) to the output (fan side) of the relay, and the cathode (negative side) to the control wire (since it's a negative trigger in the GMs), this would also eliminate the LED being turned on when the fan is being forced to spin at speed.

[CDeeZ]

If you wanted to have the fan turn on only when the fan is both commanded on by the ECM and the relay activates, you can connect the anode (positive connection) to the output (fan side) of the relay, and the cathode (negative side) to the control wire (since it's a negative trigger in the GMs), this would also eliminate the LED being turned on when the fan is being forced to spin at speed.

I wired up the LED the way you described, I think. The LED seems to work, but when the fan comes on at temp, the LED blinks for a few seconds before it lights solidly. Is this normal? I think one of my fan relays (2 relays, 2 fans, 1 relay per fan, both triggered by PCM) might be going bad. A couple times, one of the two relays has failed to turn on the fan, I grabbed them and was looking at them and one started clicking a bunch like the armature was going crazy inside, then they mysteriously started working again.

+ on LED is wired to the wire that runs from the relay to the fan (pin 87 on relay)

- on LED is wired to the trigger wire from PCM

[PJG1173]

I wired up the LED the way you described, I think. The LED seems to work, but when the fan comes on at temp, the LED blinks for a few seconds before it lights solidly. Is this normal? I think one of my fan relays (2 relays, 2 fans, 1 relay per fan, both triggered by PCM) might be going bad. A couple times, one of the two relays has failed to turn on the fan, I grabbed them and was looking at them and one started clicking a bunch like the armature was going crazy inside, then they mysteriously started working again.

+ on LED is wired to the wire that runs from the relay to the fan (pin 87 on relay)

- on LED is wired to the trigger wire from PCM

you don't have soft start enabled do you?

[RobertISaar]

i wonder.....

either soft-start or it's due to the fan spooling up.

[CDeeZ]

I didn't remember enabling soft start when I applied the code. But I went into hexeditor and checked and I do in fact have soft start enabled... Forgive my ignorance, but what exactly does softstart accomplish?

[RobertISaar]

if using a solid state relay or a good FET, then it will allow the fan speed to ramp up instead of drawing a large surge of current instantly.

if using it with a normal automotive relay, then you get the crazy relay shuttering.

[CDeeZ]

Ok thanks. I switched the hex around so I don't have softstart enabled and now the light comes on solid the first time.

Going down the highway the LED stays lit most of the time... I think I have a thermostat that needs replacing because it acts like it sticks a little bit, could this be why the fan is coming on/ staying on at highway speeds???

Or, do I need to change the fan settings?

Here's some pics for those of you who are like me and like the visuals: