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Discussion Starter #1 (Edited)
The Door Lock Control relay is very sensitive to the electrical overload and can fail if extra care is not taken when modifying the dome light with the aftermarket LED's or adding load to the dome light circuit. Here is one example of the damage that can be caused by that:



The transistor that controls the dome light overheated and that ruined the whole circuit board causing the complete loss of the electric door lock operation (this is the picture from one of the threads discussing this problem). The $400 part sure needs some extra protection even though the dome light has its own 15AMP Dome fuse.
The factory installed light bulb draws only 0.5 Amps and the relay is surely capable of handling some extra current, but by the time the Dome fuse blows the original load will be exceeded by the current about 30 times stronger. That is why we need to add another fuse to the wire from the relay to the dome light:



I bought the universal inline fuse holder and installed it in the Red/Yellow wire at the passenger side D pillar. The wires were extended to have the holder mounted in the easily accessible spot behind the tail light service cover:





The smallest fuse available to fit that holder is 2 Amps. Even though it is 4 times the current that the stock bulb draws, it will protect the relay better than the 15 Amp fuse we have. Now the ultra expensive relay is safer from the overload by the occasional short or added lighting modifications.
Now I will be installing my flood LED from Oznium with the peace of mind. It draws less current then the original bulb but with any modification the extra care is needed, especially when we play with the car's electrical system.



Here is the Interior light diagram for reference: http://scionlife.org/Scion_Docs/2004_xB_Shop_Manuals/2004 xB Wiring Manual/H_systemcircuits/IntLight.pdf
 

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Thanks for this write up!!!

Coincidentally, I was also adding some interior lights over the past 3 days. So fortunately, I read this in the morning and was able to get a mini fuse holder this afternoon and had a chance to install it tonight.


Now the $400 relay (that I didn't even know about :eek:) will be safe from these:
 

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Discussion Starter #5
Good job! I see it's pretty easy to just unwrap the harness and splice the wire right behind access cover. The lights look great, how many amps fuse did you plug?
 

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Good job! I see it's pretty easy to just unwrap the harness and splice the wire right behind access cover. The lights look great, how many amps fuse did you plug?
It wasn't too bad to do, but it is a very cramped operation, and the wire ends are at the minimum to work with. It would be much easier to remove the entire panel, but I was not motivated to do that.

Thanks, definitely makes the car more friendly at night! I am using a 2A (mini) fuse like you suggested. I bought a combo pack so I have options up to 7.5A (I think) in case that one blows too quickly, if at all.
 

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Discussion Starter #10
Do you mean OEM optional security? I don't know much about how it works, i've never seen a diagram for it- just installation instruction. What if you turn the dome light off? Will it still sound?
 

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Discussion Starter #12
Leave the strips connected but take out the bulb from the dome light and see if you still have the problem. Do you have the stock bulb there or led?
 

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Wow, very nice victor! I've avoided modding my dome cause of the $400 horror stories I've heard! Definitely doing this.
 

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Discussion Starter #18
I bought a combo pack so I have options up to 7.5A (I think) in case that one blows too quickly, if at all.
I think 2 Amps is enough for the LED's you got. I don't recommend going higher amps with the fuse. That relay becomes a time bomb once you start loading the dimming transistor. I don't have any solid data on how much load it can handle safely, but reasonably it should be OK running twice the original bulb's current. With 2 Amp fuse you limit it to up to almost 4 times the original load. If you need more then don't risk it and feed them off of a separate switch. Especially if you are living the roof lights on for long.
 

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I've been under the impression that if you replace the OEM festoon bulb with LEDs, then there is extra current available to power more LEDs since the use less to begin with.

I need to figure out how many single LEDs equal the OEM bulb...
 

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I've been under the impression that if you replace the OEM festoon bulb with LEDs, then there is extra current available to power more LEDs since the use less to begin with.

I need to figure out how many single LEDs equal the OEM bulb...
That is correct! Typically, LED systems are a fraction of the amperage of their halogen equivalent.

I am planning on doing this later in the month for the units that I used (along with a comparison of the 2 colors of "white" I have found), so I'll report back in another thread.
 
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