Repair/Replace Reverse Light

[P85MD]

My reverse light is out (not the license plate, but one of the reverse lights). I’ve removed the housing unit and taken off the LED board, is there a cheap way to get a replacement LED board without having to buy the whole inner light unit?

I’m assuming that it’s the LEDs or the board that’s broken.

 

[vcor]

You can always check eBay for a used one. If you have it apart, you might examine and test the LEDs to see if one is bad or perhaps not soldered on well. Rarely do LEDs actually fail, usually, it is the connection. Tesla almost always uses surface-mount LEDs. If one is not soldered correctly, it might create an open. If one LED is actually bad, you could remove and replace the LED. That can be a bit more tricky for those not used to dealing with surface mount components.

 

[P85MD]

I do have it apart and can examine and test the board. I don’t see any obvious issues. I went to test the LEDs / board with a multimeter and realized I don’t actually know how- that is, I don’t know where to test for resistance, or lack thereof. Any tips?

 

[vcor]

The LEDs are typically small squares surface mounted. Usually, they have two connections, on opposite sides. Set your meter to ohms, diode mode, if it has one. Diode mode has the schematic symbol for a diode, a small triangle followed by a line.

View attachment 975547
Put the probes on each side of the LED and note the reading. Switch the probes and note the second reading. One way it will show infinite resistance (often as overload or OL). The other way a good LED will show something like 0.7v (the exact number is not important, just that it shows a number in one direction). A bad LED will be shorted (0 in both directions), or open (OL in both directions).

The LEDs are in series, so if one is bad (open) none will light up. You have to test all of them.

 

[P85MD]

Super helpful. Thanks! It’s not the LEDs or the wire that connects this board. Any other ideas of what could be causing it to fail?

Or, should I just replace the whole light housing unit at this point?

 

[fholbert]

Super helpful. Thanks! It’s not the LEDs or the wire that connects this board. Any other ideas of what could be causing it to fail?

Or, should I just replace the whole light housing unit at this point?

Assume it would be cheaper buy used from a salvage yard. Google is your friend.

 

[P85MD]

Assume it would be cheaper buy used from a salvage yard. Google is your friend.

Tesla’s price isn’t too bad actually, but I’ll watch eBay for a little while too.

Not sure I understand the google comment. I’ve searched this a good bit and am at a point where asking others directly about potential fixes they have found if/when theirs stopped working seems reasonable.

 

[fholbert]

Not sure I understand the google comment. I’ve searched this a good bit and am at a point where asking others directly about potential fixes they have found if/when theirs stopped working seems reasonable.

I’d Google the part number and see if a salvage yard has one. Not sure what part you need but find a salvage one like this.

 

[dubababa]

I do have it apart and can examine and test the board. I don’t see any obvious issues. I went to test the LEDs / board with a multimeter and realized I don’t actually know how- that is, I don’t know where to test for resistance, or lack thereof. Any tips?

One of the reverse lights is out on my 2020 Model 3; I thought LEDs were supposed to last more than 10 years. How difficult was it to get the reverse light out and take it appart? I watched a video on youtube which looked pretty cumbersome. Also the guy mentioned the the modules inside the light were plastic welded together and he had to pry them appart. What did you end up doing? Great that you learned how to test LED diodes

 

[P85MD]

One of the reverse lights is out on my 2020 Model 3; I thought LEDs were supposed to last more than 10 years. How difficult was it to get the reverse light out and take it appart? I watched a video on youtube which looked pretty cumbersome. Also the guy mentioned the the modules inside the light were plastic welded together and he had to pry them appart. What did you end up doing? Great that you learned how to test LED diodes

It wasn't hard to remove- except for the upper inside (medial) bolt. I didn't have a long enough tool and my arm didn't quite fit but once I got a longer tool it was fine. I only removed the 4 bolts and took it off without removing anything else. I determined my best course was to buy a new light housing but I haven't done so yet. I have both installed since all the other lights in the housing work but I'm just using one reverse light currently.

 

[vcor]

...I thought LEDs were supposed to last more than 10 years. ...

Yep, generally they last > 50K operating hours (in a car, that should be longer than the car's lifetime). Backup LEDs are also used so little they really should last forever. Ok, two things kill LEDs. Overheat and electrical connection breaks.

Typically LEDs can handle 185°F (85°C), but they self-heat when operating. The headlights are driven at far higher power levels than backup lights, and they often have fans or metal radiators to keep them below this threshold when operating. I can't see heat being an issue with backup lights unless you parked in an oven!

Most likely one of the internal connections was poor and it failed under the vehicle's vibration and temperature cycling. Again, this shouldn't occur, but points to a minor manufacturing defect. If the car was under warranty, it would be replaced in warranty.