License plate light reset
Thread Starter
Member
Joined: Jul 2012
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2003 C32
License plate light reset
Hello All,
I just received my new LED plate lights. I plugged in to check it out, and nothing. I then plugged the factory back in, nothing (it was working prior to). If I measure voltage on the wires, it fluctuates for 0-12v, and I have an error on the guage cluster. Is there a way I can reset this? Yes, I have research, got nothing. Thanks, Mike.
I just received my new LED plate lights. I plugged in to check it out, and nothing. I then plugged the factory back in, nothing (it was working prior to). If I measure voltage on the wires, it fluctuates for 0-12v, and I have an error on the guage cluster. Is there a way I can reset this? Yes, I have research, got nothing. Thanks, Mike.
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Joined: Jan 2005
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From: Orange County
2005 C Wagon (No snickering please!)
There is no fuse for the license plate lamp. The rear SAM turns it on and off electronically. If the current is too high or too low the microprocessor will turn it off and send a message to the MFD in the instrument cluster. There is no reset other than to insert the correct lamp in the socket. The voltage turning off and on is the rear SAM interrogating the lamp.
When you removed the old festoon lamp, you might have damaged it, and it is now open. The LED must be inserted the proper direction with the +12 volts connected to the anode of the LED. Connecting the LED backward will not damage it, but it will not illuminate either. The rear SAM will not work with ordinary LED's because their current is so much lower than the incandescent lamp. Some LED's are made with an internal resistor to allow the same current as the original lamp to flow. This keeps the rear SAM happy. If the resistor is not built into the LED, one can be added externally, but they do get hot so it must be mounted where the heat will not be a problem.
When you removed the old festoon lamp, you might have damaged it, and it is now open. The LED must be inserted the proper direction with the +12 volts connected to the anode of the LED. Connecting the LED backward will not damage it, but it will not illuminate either. The rear SAM will not work with ordinary LED's because their current is so much lower than the incandescent lamp. Some LED's are made with an internal resistor to allow the same current as the original lamp to flow. This keeps the rear SAM happy. If the resistor is not built into the LED, one can be added externally, but they do get hot so it must be mounted where the heat will not be a problem.
Thread Starter
Member
Joined: Jul 2012
Posts: 216
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2003 C32
The new lights are complete LED housings. All I did was unplug the OEM light (leaving it installed) and plugged in the new light. Turned the car on to check it out, nada. Plugged the harness back into the stock, nada. Measured voltage with a DVM, and it read 0v, and then would flash 12v, back to 0... The other side works perfect. Of course, I have a check light error message. I read that I may need to have the dealer reset?
