20″ Nilight LED Light Bar Installation Subaru Outback

20″ Nilight LED Light Bar Installation Subaru Outback

Despite having relatively new replacement headlight lenses on our 1999 Subaru Outback, I decided it needed a light upgrade to help see deer better . I went with this 20″ Nilight LED Lightbar
Making the light operate legally with the factory Hi-Beam switch, meant tapping into the Subaru Hi-Beam circuit. The Subaru Hi/Lo beam circuit is a negative switch or “Low Side Switch” circuit. This complicated the install slightly.

Now normally you would assume that all you would have to do is send a signal from the headlight circuit to the relay and which would close the connection and send power to the lights. Easy right? Well this assumption causes many grief. The problem is that the only hot wire available at the headlight stays hot on both low and high beams. The high beam dipper switch switches the other end of the circuit(ground or “low side”).

A diagram of how the low side headlight switch works on the subaru.

The standard go to for installing LED lights is  a pre wired harness with a relay. I chose this one because of the heavier gauge wiring. Also the switch that came with this harness fit into one of the factory holes in the dash with only a little bit of whittling out of the inside of the dash hole.

A diagram of how I used the relay harness with the low side switched headlights. I had to  modify the LED harness:

Connection 86 had 4 wires on it. One  went directly to the battery for a ground and one to the negative for the light bar, one to ground the led on the switch and lastly one to ground out the coil in the relay. I removed the battery ground and light ground run. I grounded the light bar to the chassis directly and the battery is already grounded. That left two wires connected to  86 on the relay. One for the led on the switch and the other to ground out the coil. I grounded out the coil (86) thru the lo-side high beam.(THE RED WIRE ON THE  EXTENSION ADAPTOR IS THE HIGH BEAM GROUND)

Connection 85 was getting power directly from to the battery (30) so I removed it and tapped into the headlight common power wire. (THE BLACK WIRE  IN THE MIDDLE  ON THE HEADLIGHT EXTENSION ADAPTER is the common). The white wire that goes to the dash switch is tapped into the  common power wire at the headlight. Out of the dash switch comes the blue wire that I is connected to 85

 

I used this handy adaptor to splice into the headlight circuits so I did not have to use vampire taps on the factory harness. You can also see the relay and harness in this photo.

Dash switch

Wire harness through the fire wall