So after doing the interior LED changeover on my 2011 RX 450h, I've run into my first issue. The light on my rear driver's side door will not light up with either the LED or the standard bulb. With the door open and no bulb installed I do get 12 volts to the receptacle but nothing will light up with a bulb in.
It had been working in the past so initially I thought the LED went bad. I swapped the LED into a known working recepticle in a different door and it lit right up. I put the LED from the front door into the back door and nothing. Even after putting the original incandescent back into the back door, nothing...
I can't determine what the issue is yet, but I'm wondering if, since after all the other bulbs have been changed, if there isn't enough resistance in the entire setup anymore to allow 12 volts to remain current as soon as the bulb (LED or incandescent) is plugged in...

Anyone with any ideas as to what to try next?
What do you think Lexus would do if I took it in to the shop and explained the situation? Think they would void everything due to the use of LEDs?

 

I dont think that it is a resistance issue as I have done the same thing and have had no issues. It it was, then the bulbs would not light up at all or be very dull I would think. If the regular bulb doesnt light up then you may have an issue with the socket as that would be adding even more resistance to the circuit. Is the door switch working properly?

Test the bulbs with some leads on a charger or the battery to make sure not only do they work but that you can determine the polarity. Yes LED lights have a polarity. Sometimes they will work backwards and be dull but most times they dont work at all.

Once you know that information meter the socket. from the two contacts you should get 12v.

If the bulb is good, and you have power to the socket then if you put the bulb in correctly it should work.

 

Yes the door switch works. I can verify the socket gets 12v when the switch is open and ~0 when closed (using a multi-meter).
I've tried flipping the bulbs to check for polarity. And, like I said, swapped known good bulb with same issue and swapped possible bad bulb to a working socket and it lit up fine.

 

Most likely the socket itself is a problem-if you get 12V on the multimeter leads, attach other ends of those leads to a regular buld (instead of inserting into meter)-I bet it will light up

 

For those door lights the ground is the switched side, not the positive. Not sure if that will help or not.

 

Nope. I put my own leads on it but as soon as I put a load on it the voltage drops to 0. Full 12 volts with no load.

 

Try to swap the entire light unit with a different door, this will make sure its not the wiring.

 

I maybe way off base with this, but could there be a high resistance short? Not low enough resistance to blow a fuse, but high enough to be in series with the lamp and robbing amperage not allowing the lamp to light? You still see voltage, just no "power".

Where's an electrical engineer when ya need one?

 

Try measuring the voltage with a known-good bulb installed. I recommend putting the multimeter probes in direct contact with the bulb contacts rather than the connector itself. Assuming a fully charged battery, you should see approximately 13.8V.

If you see close to zero, it means that, as someone else suggested, that there is high resistance somewhere between the bulb connector and the battery. The most likely place for this to happen is where the connector (socket) terminal is attached (either soldered or crimped) to the wires.

Try wiggling the wires around with the bulb installed and see if you see any change in measured voltage. This might help isolate where a problem might exist.

Good luck!

 

Well, I haven't put too much more time into it over the weekend. But I did try using know good bulbs etc. I removed the harness and added my own leads right from the wire terminals, didn't work. As soon as I put a bulb on V drops to ~0.

I'm kind of at wits end with this one. It's not that big of deal (aesthetically) to keep doing everything I have been doing... My geek mind keeps working on it and wondering what has happened and if it will cause any long term issues.