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Hello Everyone,

I'm at wit's end with this and need help. I have a 2009 Sienna that the Dome light fuse keeps blowing. It used to be intermittent but now it appears to be constant(which in some ways I consider a good thing). I have completely disconnected the interior light switch and it's still blowing the fuse. I have a Haynes manual with all the wiring diagrams but understanding it and accessing the integration relay hasn't been easy. Anybody out there who would like to point me in the right direction?
 

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Hi 500. Your right, an intermittent to a hard failure is a step in the right direction. I have an 04 and if the lighting system is about the same your going to have to pop apart a lot of lights and panels. On my schematics the Dome 10A circuit branchs out like an octopus to feed 12V to ALL the lamp sockets, vanity lights etc, etc. Look at your diagrams to see if they keep the same setup. This line does not even go through the main switch. This line is obviously shorted to ground either at a lamp assembly or this network of wiring. Intermittent at first until vibration moved or wore away insulation to create the hard failure. You could use a meter on Ohms scale but a simple 12V lamp wired in place of the Dome fuse should light to give an indication that the line is at a hard ground shorted condition. When the short is removed the lamp should go off. Or get a BIG pack of fuses to keep popping through for testing. Remove and disconnect all the interior lamp units one at a time attached to this line. If the fault goes away with one bingo, thats the one or the wiring in its immediate vicinity. If you get all the lamp assemblys that are easily disconnected out and its still shorted then its in a remaining lamp assembly or a wiring harness problem. Then you will have to find the numerous junction connectors to disconnect to break this distribution circuit apart until the short goes away. Might be in a door, front or rear body of the van, left or right side, etc. A process of elimination. Good luck!
 

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Same problem on 2008 Sienna--fuse would blow. Took all bulbs out except above driver. Replaced fuse every few days. Undid liftgate (back door) panels and investigated wiring. Slammed doors, wiggled wires, etc. Would work for a day, then blow. Or blow right away. So I replaced the fuse with a 10 Amp circuit breaker to investigate. Lights would come on and off randomly. Kept it in there a couple of weeks. Drove 300 miles last Sunday, no dome lights but no problems. Thursday AM it would not start--bad smell inside. The circuit breaker apparently broke, completed the circuit, and melted the wiring. The dome light circuit somehow is connected to everything else. Toyota states $13,000 to fix, and insurance will not cover it as a loss. Still have $10K to pay on it. Will get $1500 maybe on a trade in for another car (which I was shocked at since it is worthless now--they apparently will part it out), so we will have essentially 2 car payments for one different car. Sad day. Be forewarned. Just leave the fuse out and get a flashlight. Cars are too complicated--and expensive-- these days!
 
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