Tested LED License Plate Resistors. - Page 2 - 2014+ Jeep Cherokee Forums
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post #11 of 42 (permalink) Old 01-14-2016, 01:46 AM Thread Starter
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Originally Posted by Dino View Post
The mini license plate light came with ground wire and hot wire and it had a built in resistor. Ran the wiring through the existing light bulb aera and tapped into one of the lights. Both bulbs still work but the bar puts out so much light you won't be able to tell. All and all took about 30 to 45 mins.
Do you have ESS? Do you get errors when ESS turns the engine on or off?

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post #12 of 42 (permalink) Old 01-16-2016, 10:13 AM
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I just did the same update on my car and am getting errors on startup for the license plate. Haven't upgrading the back up lights yet. These errors seem minor and not that bad but I'm a few days in lol

Did you end up testing the resistors on the reverse lights? What was the outcome there?

I also have ESS on my car so it sounds like this won't be a fix for me. I wonder why you are only getting the error when starting ESS? It doesn't make sense, unless the car is monitoring things differently?
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post #13 of 42 (permalink) Old 01-16-2016, 10:16 AM
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Too bad variable resistors couldn't be used so they could be dialed in.
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post #14 of 42 (permalink) Old 01-20-2016, 01:17 PM Thread Starter
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Update: They've basically failed completely at this point.

I haven't changed anything, but now they're tossing errors at start up.

I pinged @Wisconsin Mike, maybe he can help / shed some light?

His: 2015 Cherokee TH: Brilliant Black; V6
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post #15 of 42 (permalink) Old 01-20-2016, 01:18 PM Thread Starter
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Originally Posted by IronGOOS3 View Post
I just did the same update on my car and am getting errors on startup for the license plate. Haven't upgrading the back up lights yet. These errors seem minor and not that bad but I'm a few days in lol

Did you end up testing the resistors on the reverse lights? What was the outcome there?

I also have ESS on my car so it sounds like this won't be a fix for me. I wonder why you are only getting the error when starting ESS? It doesn't make sense, unless the car is monitoring things differently?
I haven't tried them in the reverse lights. I was just continuing to test them in the license plates lights. As of my latest update, they seem to have failed completely. I get errors at start up now.

His: 2015 Cherokee TH: Brilliant Black; V6
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post #16 of 42 (permalink) Old 01-20-2016, 01:26 PM Thread Starter
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Originally Posted by Duke2015 View Post
i just got mine in the mail, the leds im using are ultra low power, so the 3.5w resistors do nothing and still got a warning light. no ess here either. going to put in higher powered led t10s into the resistors to see if they work
I had to use two resistors, one on both lights of the license plate to see any change in the errors.

His: 2015 Cherokee TH: Brilliant Black; V6
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post #17 of 42 (permalink) Old 01-20-2016, 08:16 PM
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Hey @gravitywell,

Interesting that you bring this up... I was planning on tinkering on the backup lights myself!

It makes sense to me that the ESS system *could* cause errors because the Jeep system voltage will fall while the engine isn't running. The charge voltage while the engine is running is around 14.4V, but the battery voltage is quite a bit lower (probably around 12.5V with only small accessories on). The reason that voltage change is important here is because when you insert a resistor, the current that the resistor draws changes depending on the voltage.

Remember waaaay back from school, Ohm's law is E=IR.
E is electromotive force which is the voltage.
I is the current flow in Amps.
R is the resistance in Ohms.

So if the resistance is held constant and the voltage goes down, the current also goes down accordingly. Which means that when the ESS system shuts off the engine and the system voltage falls from 14.4V down to around 12.5V (that's about a 13% drop), then the current will also fall by the same percentage.

If the combination of LED current plus resistor current is near the borderline for where the lamp out indicator is, then simply dropping the current by 13% might easily be enough to trip the sensor.

There's two ways to attack this problem...

1) Figure out where the threshold in the Jeep is and make sure the total current is somewhat over that even at the minimum system voltage. I can probably help out here by using the same technique I used for the headlights. It only takes time!

2) Figure out how much current the stock incandescent lamp draws and make sure that the LED plus resistor draws a similar amount of current. This is just inserting an ammeter in series with the stock lamp and measuring the current both with the engine running and with it off. Then measure the amount of current that the LED draws. Subtract to find the difference that you need. Using Ohms Law, calculate the resistance needed to create that much current flow.

It's interesting that you're setup is getting progressively worse. It started with no errors, then started having ESS errors, now it has errors all the time. Makes me wonder if your resistors are overheating and opening up or maybe there is a corroding connection. Can you measure the resistance of your Amazon resistor? Do you know what the resistance is supposed to be?
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post #18 of 42 (permalink) Old 01-21-2016, 11:22 AM Thread Starter
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Originally Posted by Wisconsin Mike View Post
Hey @gravitywell,

Interesting that you bring this up... I was planning on tinkering on the backup lights myself!

It makes sense to me that the ESS system *could* cause errors because the Jeep system voltage will fall while the engine isn't running. The charge voltage while the engine is running is around 14.4V, but the battery voltage is quite a bit lower (probably around 12.5V with only small accessories on). The reason that voltage change is important here is because when you insert a resistor, the current that the resistor draws changes depending on the voltage.

Remember waaaay back from school, Ohm's law is E=IR.
E is electromotive force which is the voltage.
I is the current flow in Amps.
R is the resistance in Ohms.

So if the resistance is held constant and the voltage goes down, the current also goes down accordingly. Which means that when the ESS system shuts off the engine and the system voltage falls from 14.4V down to around 12.5V (that's about a 13% drop), then the current will also fall by the same percentage.

If the combination of LED current plus resistor current is near the borderline for where the lamp out indicator is, then simply dropping the current by 13% might easily be enough to trip the sensor.

There's two ways to attack this problem...

1) Figure out where the threshold in the Jeep is and make sure the total current is somewhat over that even at the minimum system voltage. I can probably help out here by using the same technique I used for the headlights. It only takes time!

2) Figure out how much current the stock incandescent lamp draws and make sure that the LED plus resistor draws a similar amount of current. This is just inserting an ammeter in series with the stock lamp and measuring the current both with the engine running and with it off. Then measure the amount of current that the LED draws. Subtract to find the difference that you need. Using Ohms Law, calculate the resistance needed to create that much current flow.

It's interesting that you're setup is getting progressively worse. It started with no errors, then started having ESS errors, now it has errors all the time. Makes me wonder if your resistors are overheating and opening up or maybe there is a corroding connection. Can you measure the resistance of your Amazon resistor? Do you know what the resistance is supposed to be?
I have a multi-meter back at my parent's house. I currently don't have any way to test, at all.

Here are the resistors: http://amzn.com/B00CVYU01C

I don't see any indication of what the resistance is. I'll see if I can contact the vendor.

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post #19 of 42 (permalink) Old 01-21-2016, 11:55 AM
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I can certainly do some of this myself. Like I said, I was planning on installing brighter LED back-up lights at some point, which will hopefully improve the back-up camera operation. So my plan is to use my variable load to discover where the lamp out threshold is. Then I can just replace the variable load with the stock lamp and that'll show me what the stock lamp draws. After that, it's just maths and Amazon.
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post #20 of 42 (permalink) Old 01-21-2016, 01:34 PM Thread Starter
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Originally Posted by Wisconsin Mike View Post
I can certainly do some of this myself. Like I said, I was planning on installing brighter LED back-up lights at some point, which will hopefully improve the back-up camera operation. So my plan is to use my variable load to discover where the lamp out threshold is. Then I can just replace the variable load with the stock lamp and that'll show me what the stock lamp draws. After that, it's just maths and Amazon.
RVinyl responded, it is 10ohm.

His: 2015 Cherokee TH: Brilliant Black; V6
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