Light bar install (dimmer switch)

2021 TOYOTA SIENNA HYBRID
1,000 MILES • 4 CYL • 4WD • AUTOMATIC
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ALASKAWOLF
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Hello everyone from Alaska here. We get very dark long winters and I am trying to install a LED light bar and some Hella headlamps on the van. I have wired many lights before on older vehicles by hooking into the dimmer switch by either plugging right into the headlight harness tapping into the wires there or using a fuse box.
Problem is I can’t find the fuse labeled driving lights or high beam lights and I have tried to test the harness that connects into the back of the headlight assembly switching high beam and low beam and the voltage on either of the wires doesn’t change. (One is ground, another one runs about 7v and the other one runs at 12 V.)
I guess I’m a bit thrown off because usually you have your ground and then whenever you have your high beams off one wire will read zero and the other one will have whatever volts you’re using for your low beam, and then when you turn your high beams on, your low beam will read zero and your high beam will read whatever you’re using for your high beam and that’s how you identify which one to tap into. Can’t get this result with this van..
Has anybody successfully wired aftermarket lights into the van listed above XSE? If so can you please tell me how you did it.
Feb 7, 2021 at 2:24 AM
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STEVE W.
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Welcome to the world of fully integrated lighting. The new Sienna uses lighting "modules" that don't have a high/low beam feed, only a computer signal into the modules control chip telling it to switch internally from low to high beam. Wiring wise it has a power feed, ground and the signal wire that tells it what to do. There are a few Euro cars with the same scheme in them. About the only way to add extra lighting would be the old fashioned switch method until someone makes an interface box that can use the control signal, which may take a while as it wouldn't be a big seller.
The only other idea would be to open one of the light modules up and determine where the high beam feed to the lamp itself is and tap that to control a relay outside the module. Not something I would say to do simply because there is no data on the loading ability of the internals, the extra drain of a relay could be enough to damage the circuitry.
Even the dimmer switch is useless because it does nothing but toggle the control input to the module to tell it to switch modes.

Feb 7, 2021 at 4:00 AM