Reverse lights getting constant 3-6v with empty bulb socket

itsmeakay

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Hi,

I own a 2009 Mustang GT. Recently, replaced the stock reverse lights with white LED lights. They come on fine as expected. But observed following issue - My recently replaced digital system Alpine ILX W650 with android auto connected to a newly added rear view camera, that was working fine with stock bulbs in the reverse light sockets, now, always remains in rear camera view mode after replacing stock reverse lights with new LED ones.

The android auto is connected to a reverse wire (yellow white wire on the passenger side) for it to get the signal for reverse gear and turn on camera automatically. With stock bulbs, this wire has 0v. So the Android auto reverse camera functionality works fine as expected. But, when I put the new LED or keep the socket empty without a bulb, this wire keeps on getting around 3-6v, on both driver and passenger side reverse light sockets. This makes the android auto think that we are always in the reverse mode.

In order to just brute force test by pulling out SJB fuses from engine side box - I tried following - removed SJBs 59, 62, 63, 67. but the reverse light sockets still get around 3v (less than before, but not 0v) when no bulb in the sockets.

Is it expected for the reverse light sockets to get more than 0v when empty or fit with LED bulbs? Why is the issues not observed with stock bulbs but only with the new LED ones.
If this is a problem, I need suggestions to fix it.
 

Juice

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Yes.
What you are measuring is voltage leaking through solid state switching. Your HU is detecting this voltage since you removed the resistance of incandescent bulbs. I bet you can see your LED bulbs glow faintly at night when the car is parked.
Adding resistors is the only fix. Or put the regular bulbs back in.
 

itsmeakay

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@Juice
Thanks for the reply.

I did not observe any faint glow (observed the LED bulb without any cover on it) when car is off (even at night). But I do see, why you are saying that there should be a faint glow. May be I will double check once.

Regarding - adding resistors, how should I go about it? Are there pluggable resistance units available on e-commerce websites that I can put between the LED and the reverse light socket? Or I have to build something by self? If by self, then any pointers on how to go about making it by self?

I really dislike the old yellowish stock reverse lights and I wish to put white 6000K bulbs instead. I don't care if it is LED or not.

Thanks in advance for any further help.
 

Juice

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I went the resistor route. Mainly because of hyperflash of turn signals. IIRC, you do not have to match the incandescent bulb's draw. Just enough resistance to trick the SJB. I forget what ohm resistors I used, but they are very small in size, can easily be added at the connector. They do get hot to the touch, but no other issues. Had that setup for years. I have a few resistors left somewhere, if I can find them, I will post the ohms.
 

redfirepearlgt

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Properly sized the resistors should not get hot in this application. By sizing I mean wattage rating and required resistance, not simply resistance. A 1/4 or 1/2 watt resistor will likely not suffice safely.

Using your meter measure the resistance across the reverse lamp bulb. This is your total resistance you are targeting. Then take a resistance reading across the LED lamp. You will need to observe polarity when doing this so the LED forward biases. Then subtract that resistance from the resistance of the bulb and you know the resistor ohm rating you are seeking. Next take the ohm value of the bulb and use the following formula to determine total wattage E^2/R or Voltage squared divided by resistance.

Voltage would be that which is measured with the reverse lights on. (likely 12-13.8vdc)

Finally you will also calculate the wattage (unless it is known) of the LED in the same manner. Subtract the wattage value from the total wattage calculated for the tungsten bulb. This will give you the wattage rating you need for the resistor used. Now you have a properly sized resistor that will properly dissipate the heat without burning up or getting hot to the touch.

Installing a larger than needed wattage value resistor is fine. it is only when using too small a resistor that there is an issue. Its the same as trying to run 22 gauge wire to pull 10 amps of current across it. It will turn into a heating coil.
 
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@Juice
Thanks for the reply.

I did not observe any faint glow (observed the LED bulb without any cover on it) when car is off (even at night). But I do see, why you are saying that there should be a faint glow. May be I will double check once.

Regarding - adding resistors, how should I go about it? Are there pluggable resistance units available on e-commerce websites that I can put between the LED and the reverse light socket? Or I have to build something by self? If by self, then any pointers on how to go about making it by self?

I really dislike the old yellowish stock reverse lights and I wish to put white 6000K bulbs instead. I don't care if it is LED or not.

Thanks in advance for any further help.

Just snap on one of these between the + and - wires leading to the backup lights. It is quick and easy.

61Gzg82ViSL._AC_SL1200_.jpg


https://www.amazon.com/iBrightstar-50W-6ohm-Load-Resistors/dp/B07HF47RV9/ref=sr_1_4?crid=48DTXS2WL814&keywords=resistors+for+led+lights&qid=1654818511&sprefix=resistors+f,aps,92&sr=8-4
 

GriffX

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Does a CAN bus compatible LED fix this issue? (I was searching for an LED for the 3rd brake light)
 

DieHarder

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This.....though I would recommend soldering the wires vice using those clips which I haven't had much luck using. Sometime they work but ones I've used typically develop issues later on.
 
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This.....though I would recommend soldering the wires vice using those clips which I haven't had much luck using. Sometime they work but ones I've used typically develop issues later on.

I have not had any problems with those connectors. I wrap them in electrical tape and they are good to go. You do need to use the correct clips for the gauge wire you are spicing and I use a pliers to "set" the metal splicer completely before I close them. I solder some connections but these are ideal for this application.

https://www.electricalbasics.com/blog/Use-Tap-Splicers-to-Connect-Electrical-Wires
 

Juice

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Agree. Would you like to make product reviews to some free LED light bulbs? If you want to please email or PM me.
Na, I wouldnt want to put any review-bots out of a job!
:lol:
 

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