Service engine soon indicator

alloy

alloy

Dan, Retired old fart
H-M Supporter Gold Member
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I'm still working on putting the LS into the nova and ran across this in the swap harness instructions. I'm told if I use an LED the computer will throw a code.

mil lamp do not use led.jpg

I got this great looking indicator light (LED of course) that goes with the other lights for the automoeter dash and I want to use the indicator I have. I've only found one non LED indicator light and it's much bigger. The indicator lights I have are black and you can hardly see them in the dash since it's black also.

Back in the day as I recall there were problems with LED working and I think they solved it using a resistor. Can I do something like that in this situation?
ses indicator.jpg
 
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Depends on the voltage required for the LED. Many instructions on the web.
 
it's a 12 volt DC system
 
Need to know if the led uses 1.5 vdc or otherwise. A 1/2 watt resistor is required as a minimum.

V--------- is the voltage you will use to power the led
Vfled---- is the forward voltage of your led
Vfd------- is the forward voltage of your diod
Imax---- is the maximum voltage that your circuit can take so that would be your LEDs operation current
 
pdentrem said:
Need to know if the led uses 1.5 vdc or otherwise. A 1/2 watt resistor is required as a minimum.

V--------- is the voltage you will use to power the led
Vfled---- is the forward voltage of your led
Vfd------- is the forward voltage of your diod
Imax---- is the maximum voltage that your circuit can take so that would be your LEDs operation current
Click to expand...
That only limits the current that the LED sees to the amount it needs, typically 20ma. I suspect that the reason that an incandescent bulb is specified for the MIL is so that the computer can sense that the bulb is out and throw a code.
 
I have gotten around the no LED issue on other things, by using a small relay to turn the LED on.

You might also be able to use a resistor bypassing the LED, like is used for the charging light on older delco alternators, to get LEDs to work. How to figure out what value, is beyond me.

jeffkash said:
That only limits the current that the LED sees to the amount it needs, typically 20ma. I suspect that the reason that an incandescent bulb is specified for the MIL is so that the computer can sense that the bulb is out and throw a code.
Click to expand...
Not sure, but most of the older computers needed the CEL light to throw a code.
 
Yeah you probably need a series resistor of about 1k with the led and possibly a parallel resistor to +12v of I would guess maybe around 500 ohm
It looks like what is called an "open collector" output which acts like a switch to ground, but it may need a certain amount of current flow to work properly
-Mark
Something like this:
 

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Here is a topic about your questions and a reference to another posting. Answers the question with an interesting twist.

MIL light wiring issue - LS1TECH - Camaro and Firebird Forum Discussion

Conversions & Swaps - MIL light wiring issue - well, I decided to pick up a check engine light for the dash, so i drilled a 5/16 hole connected the brown wire from comp. harness (psi harness) to light, then another to 12v. my problem is when I start engine the light comes on for 2-3 seconds and...
ls1tech.com
 
I appreciate al the replies. I understand the 500 ohm resistor. I think I can get one off Amazon since radio shack is gone.

Anohter idea, since the ECM is looking for the light, how about giving the ECM the light, and wiring the LED in with the light and use the LED, and just cover up the light? I have plenty of spare lights.

Good or bad idea?

I just looked at the specs for the LED indicator. It says resistor built in.

Mounting Cut Hole: 12mm (1/2")
Head Diameter: 15.80mm (0.62")
Bulb Type: LED
LED Color: Amber
Lamp Voltage: 12V DC
Current Rating: 15mA
Wire Length: 8"
Wire Gauge: 18
Bezel Color:Black
Body Material : Aluminum Black
Panel Thickness: 1-10mm
Description:Check Engine
* Not Polarity Sensitive
Resistor Built-in
 
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