LED right side turn signal bulbs work for a few seconds then stops working?

JITHIN MATHEW

MEMBER
2011 MERCEDES BENZ C300
3.3L
V6
4WD
AUTOMATIC
93,000 MILES

I had upgraded the rear turn signals to some Auxito LED bulbs that is equipped with CANBUS. I noticed that the right bulb works for a few seconds and then it stops and I immediately get a bulb out error on the cluster. The left bulb works with no issues, it’s just the right that’s having an issue. I thought it was the bulb, so I put another brand new bulb in and it still does the same thing. When I lock and unlock the car both bulbs work with no problem. I put the old incandescent bulb back into the right side and it works with no issues. Has anyone had this problem before?

6 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

I'm not sure how that is tied into the can-bus, but I can tell you that LEDs draw much less power than incandescent bulbs. That is likely the cause of the bulb-out indicator turning on.

When you installed them, did you also use a resister for each of the lights? Signal lamps will require a resister. I know that some aftermarket assemblies have a built-in resistor. Do you know if that is the case?

Let me know.

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Monday, January 16th, 2023 AT 6:18 PM

JITHIN MATHEW

MEMBER
62 POSTS

Yes, I am aware of the LED bulbs drawing less current. The weird part is that the left LED bulb that I installed has been working with no issues or bulb out warning. The car is shutting off the right bulb for some reason every time I activate the right blinkers. When I lock or unlock the car with my keys, both LED bulbs work.

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Monday, January 16th, 2023 AT 6:53 PM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

I just went through wiring schematics and found that the left and right-side signals get power from two different pins at the SAM module (Signal Acquisition Module). If there the left power supply has a bit more resistance in the wire, that could allow the circuit to continue working. See pic below.

I feel it you would place a resister at the right rear signal lamp, that would eliminate the bulb out and failure of the right side.

Let me know.

Take care,

Joe

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Monday, January 16th, 2023 AT 8:05 PM

JITHIN MATHEW

MEMBER
62 POSTS

The bulbs have built in CANBUS and load resistors.

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Monday, January 16th, 2023 AT 9:21 PM

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

The light out warning system must be seeing a slight voltage variation with the LED of the right side. It works correctly with the stock bulb, correct? Have you tried more than two new LED's? It could be a bad batch from the manufacturer.