Besides utilizing that bay area to mount your relay and ballast, is there really any reason to pull the whole battery and tray out?
Morimoto HID Kit Install
I decided to do a write-up on how to install the Morimoto Elite HID system in the 2015 OB. The install is pretty straightforward; I’d say about 2/10 difficulty. Basic automotive electrical system knowledge his helpful but not required – it’s pretty hard to screw this up. The point of this is purely educational. I’m not here to start a debate about HID’s or retrofitting, please save that for another forum.
So far I'm very happy with this kit. The cutoff isn't as great as a true retrofit, but it's not terrible for being set in halogen projectors. It's certainly better than the halogen setup.
The dreaded LIN (local interconnect network) sensor:
Starting in 2015 Subaru starting putting a LIN sensor on their cars, including the OB. This sensor is on the negative battery post and feeds information back to the ECU about the load on the electrical system. Because of this, any ground additions to the electrical system need to be added behind this sensor so they can be actively monitored. You should never ground anything to the battery on any car with a LIN sensor. I haven’t heard any actual reports of issues with Subaru’s, but supposedly this can negatively affect gas mileage or worst case, kill your ECU. I’ve never seen a confirmed case of either of these scenarios. The bottom line is that you’ll need to use factory grounds on the frame. Good news is there are quite a few under your hood, so don’t sweat it.
I talked to two Subaru mechanics regarding the LIN sensor and grounding aftermarket electronics. They both said that as long as you didn’t ground directly to the negative terminal on the battery you’d be fine. I’ve been using this setup in my car for about 3 weeks now with no ill effects. My gas mileage is consistent at around 26mpg average, no check engine lights. I have pulled codes twice to see if there are any inactive stored codes and there is nothing.
Why not use a direct plug system? (Or, why relays are awesome):
I’m not here to badmouth any HID system, nor am I affiliated with any company that makes HID’s. I am, however, paranoid about modifying a brand new car – especially when it comes to one with a rather complicated computer and electrical system. There are a ton options out there that plug right into your existing plugs with no external ground of power needed. Problem is, your non-HID equipped Subaru was never meant to handle the load created by HID’s. They draw significant power when starting up, and require a smooth, consistent power draw. I personally wouldn’t risk putting this load on the OEM harness.
Instead of loading the harness with the draw needed for the power and ground, you can let a relay do the heavy lifting. Simply put, a relay uses a small current to switch a much larger current on or off. How this works in the HID scenario is as follows:
You plug your stock H11 (the connector the plugs into the low beam bulb) into the relay harness. The relay harness is wired directly to your positive battery post and grounded twice to the frame. The relay directly powers the ballasts. As soon as the relay senses the low current from the stock plug when you turn on your headlights, it switches the power to onto the heavy duty harness wired directly to the positive battery terminal. This powers the HID completely inside an isolated and fused circuit that was meant to handle the excessive load. No load or risk to the stock harness at all.
The best part is that you don’t need to cut any wires; everything is still completely plug and play. It just takes a little more time and effort to install. The relay is essentially your insurance policy that protects the OEM system. It’s fused and redundant, and in the off chance it went belly up you’d only be out the $30 to replace it.
What you’ll need:
I bought my kit from TRS, The Retrofit Source (https://www.theretrofitsource.com). Here is the direct link for the kit I bought. You’ll need a decent variety of heavy duty zip ties (not the reusable ones) and double sided mounting tape. You’ll also need a basic tool set – sockets, deep sockets, extensions, ratchets and side cutters are very helpful.
Make sure and chose the H11B bulbs. This is important! The regular style will not fit in your OB housing – the B style has a larger tab which orientates the bulb in the correct direction.
H11: Morimoto Elite HID System - http://www.theretrofitsource.com/hid-systems/morimoto-elite-hid-system-h11.html#.VSNFj2d0zDc
HID Ballasts
-2 x Morimoto XB35 (35W)
Ballast Igniters
-2 x Morimoto XB Igniter (AMP)
Compatible H11 HID Bulbs
-2 x H11B: XB 5500K (whatever color temp you prefer, I chose 5500K)
Harness
-1 x HD Relay: H11/H9/H8
Extension
-1 X 9006 Extension Cords, pair. Not required, but makes the install so much more clean and easy –
http://www.theretrofitsource.com/components/harnesses/9006-extension-cords.html#.VSNMMmd0zDc
Once you have everything make sure you have a couple of hours and a few beers to complete the job. Let’s start! For clarification, the left side is the driver’s side; the right side is the passenger’s side.
Step One – Remove the Battery and Plastic Battery Tray:
I didn’t take pictures of this step. If you are uncomfortable doing this or cannot figure out how to remove it, please stop and ask yourself if you should actually be doing the install.
If you want to disconnect your DRL’s this is a good time to do it since everything is out of the way. Once you remove the battery and tray, this is the area you’ll be working in.
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Important! Once you reconnect the battery you’ll notice that you can’t roll down the passenger window from the driver’s side control. This is supposedly a ‘feature’ and is noted in the user manual. To fix this, roll down the passenger window down completely from the passenger side control. When rolling it back up, continue to hold the button up for a moment after the window is completely closed. You’ll then be able to use the driver’s side control again. This will happen every time the car completely loses power and has nothing to do with the HID system.
If you want to disconnect your DRL’s this is a good time to do it since everything is out of the way. Once you remove the area, this is the area you’ll be working in.
Step Two – finding a home for left side ballast and relay:
I’m big on having clean, neat wiring. I wanted the relay and ballast well hidden and out of the way. They also need to be in a place where they are secure and unlikely to contact large amounts of water or vibrate excessively. Finding places to put the components was harder than expected as I didn’t want to drill new holes or make any permanent changes under the hood.
Fortunately, there is a nice void under the battery between the support beam and windshield washer reservoir. I was able to fit both the left side ballast and relay in this spot. The relay needs to be close to the battery as the lead goes directly to the positive terminal.
The relay fits nicely into the groove under the battery support beam. Since the beam is tapered, you have to use two zipties to make sure it doesn’t slide off.
![]()
Once you get the relay secured you are ready to put the ballast in. Put some double sided tape on your ballast and slide it under the relay. Once in place, press it firmly onto the washer fluid reservoir so it’s secure. Make sure you have enough clearance to plug in your connectors! It will be a tight fit! Once in, connect the plugin to the input for the relay and the output to the amp. They only fit in one way. Make sure the seals seat securely and the retainers click on.
![]()
Step Three – Running Wires:
You’ll notice small white plugs around your engine bay that are attached to the frame using a single screw. They will have multiple wires running to them. These are the factory grounds and are a great place to ground the relay to. You’ll need a 10MM socket with an extension to get to it. Undo it, connect your ground and screw it back in securely.
![]()
The best place to run the long wire to the right side ballast is under the plastic cowling that runs along the front of the car directly under the hood. This way it’s completely out of the way of any moving parts and heat sources. Unfortunately it’s not quite long enough to come out the other side. This is where you’ll need the 9006 extension cord. Connect the extension and run it out the other side towards the right headlight.
![]()
The best place I found to mount the ballast was up inside the right fender. There is a slight flat spot high up and it mounts perfectly using 2 sided tape. The amp can mount to the inside of the body support also using 2 sided tape.
![]()
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The last thing you need to do is run the ground for the right side ballast. Fortunately, you’ll find a factory ground point in the right side engine bay down under the air intake box. It's also a 10mm.
![]()
Now you can install the bulbs. Make sure and wipe them off carefully with the alcohol pads. They only fit in the housing one way.
You’re almost done! At this point you can hook up all the weatherpack connectors to the ballast and amps if you haven’t already done so and reinstall the battery. Make sure you have everything out of the engine bay, check your grounds and connections and fire em’ up!
![]()
![]()
![]()
So far I'm very happy with this kit. The cutoff isn't as great as a true retrofit, but it's not terrible for being set in halogen projectors. It's certainly better than the halogen setup.
The dreaded LIN (local interconnect network) sensor:
Starting in 2015 Subaru starting putting a LIN sensor on their cars, including the OB. This sensor is on the negative battery post and feeds information back to the ECU about the load on the electrical system. Because of this, any ground additions to the electrical system need to be added behind this sensor so they can be actively monitored. You should never ground anything to the battery on any car with a LIN sensor. I haven’t heard any actual reports of issues with Subaru’s, but supposedly this can negatively affect gas mileage or worst case, kill your ECU. I’ve never seen a confirmed case of either of these scenarios. The bottom line is that you’ll need to use factory grounds on the frame. Good news is there are quite a few under your hood, so don’t sweat it.
I talked to two Subaru mechanics regarding the LIN sensor and grounding aftermarket electronics. They both said that as long as you didn’t ground directly to the negative terminal on the battery you’d be fine. I’ve been using this setup in my car for about 3 weeks now with no ill effects. My gas mileage is consistent at around 26mpg average, no check engine lights. I have pulled codes twice to see if there are any inactive stored codes and there is nothing.
Why not use a direct plug system? (Or, why relays are awesome):
I’m not here to badmouth any HID system, nor am I affiliated with any company that makes HID’s. I am, however, paranoid about modifying a brand new car – especially when it comes to one with a rather complicated computer and electrical system. There are a ton options out there that plug right into your existing plugs with no external ground of power needed. Problem is, your non-HID equipped Subaru was never meant to handle the load created by HID’s. They draw significant power when starting up, and require a smooth, consistent power draw. I personally wouldn’t risk putting this load on the OEM harness.
Instead of loading the harness with the draw needed for the power and ground, you can let a relay do the heavy lifting. Simply put, a relay uses a small current to switch a much larger current on or off. How this works in the HID scenario is as follows:
You plug your stock H11 (the connector the plugs into the low beam bulb) into the relay harness. The relay harness is wired directly to your positive battery post and grounded twice to the frame. The relay directly powers the ballasts. As soon as the relay senses the low current from the stock plug when you turn on your headlights, it switches the power to onto the heavy duty harness wired directly to the positive battery terminal. This powers the HID completely inside an isolated and fused circuit that was meant to handle the excessive load. No load or risk to the stock harness at all.
The best part is that you don’t need to cut any wires; everything is still completely plug and play. It just takes a little more time and effort to install. The relay is essentially your insurance policy that protects the OEM system. It’s fused and redundant, and in the off chance it went belly up you’d only be out the $30 to replace it.
What you’ll need:
I bought my kit from TRS, The Retrofit Source (https://www.theretrofitsource.com). Here is the direct link for the kit I bought. You’ll need a decent variety of heavy duty zip ties (not the reusable ones) and double sided mounting tape. You’ll also need a basic tool set – sockets, deep sockets, extensions, ratchets and side cutters are very helpful.
Make sure and chose the H11B bulbs. This is important! The regular style will not fit in your OB housing – the B style has a larger tab which orientates the bulb in the correct direction.
H11: Morimoto Elite HID System - http://www.theretrofitsource.com/hid-systems/morimoto-elite-hid-system-h11.html#.VSNFj2d0zDc
HID Ballasts
-2 x Morimoto XB35 (35W)
Ballast Igniters
-2 x Morimoto XB Igniter (AMP)
Compatible H11 HID Bulbs
-2 x H11B: XB 5500K (whatever color temp you prefer, I chose 5500K)
Harness
-1 x HD Relay: H11/H9/H8
Extension
-1 X 9006 Extension Cords, pair. Not required, but makes the install so much more clean and easy –
http://www.theretrofitsource.com/components/harnesses/9006-extension-cords.html#.VSNMMmd0zDc
Once you have everything make sure you have a couple of hours and a few beers to complete the job. Let’s start! For clarification, the left side is the driver’s side; the right side is the passenger’s side.
Step One – Remove the Battery and Plastic Battery Tray:
I didn’t take pictures of this step. If you are uncomfortable doing this or cannot figure out how to remove it, please stop and ask yourself if you should actually be doing the install.
If you want to disconnect your DRL’s this is a good time to do it since everything is out of the way. Once you remove the battery and tray, this is the area you’ll be working in.
Important! Once you reconnect the battery you’ll notice that you can’t roll down the passenger window from the driver’s side control. This is supposedly a ‘feature’ and is noted in the user manual. To fix this, roll down the passenger window down completely from the passenger side control. When rolling it back up, continue to hold the button up for a moment after the window is completely closed. You’ll then be able to use the driver’s side control again. This will happen every time the car completely loses power and has nothing to do with the HID system.
If you want to disconnect your DRL’s this is a good time to do it since everything is out of the way. Once you remove the area, this is the area you’ll be working in.
Step Two – finding a home for left side ballast and relay:
I’m big on having clean, neat wiring. I wanted the relay and ballast well hidden and out of the way. They also need to be in a place where they are secure and unlikely to contact large amounts of water or vibrate excessively. Finding places to put the components was harder than expected as I didn’t want to drill new holes or make any permanent changes under the hood.
Fortunately, there is a nice void under the battery between the support beam and windshield washer reservoir. I was able to fit both the left side ballast and relay in this spot. The relay needs to be close to the battery as the lead goes directly to the positive terminal.
The relay fits nicely into the groove under the battery support beam. Since the beam is tapered, you have to use two zipties to make sure it doesn’t slide off.
Once you get the relay secured you are ready to put the ballast in. Put some double sided tape on your ballast and slide it under the relay. Once in place, press it firmly onto the washer fluid reservoir so it’s secure. Make sure you have enough clearance to plug in your connectors! It will be a tight fit! Once in, connect the plugin to the input for the relay and the output to the amp. They only fit in one way. Make sure the seals seat securely and the retainers click on.
Step Three – Running Wires:
You’ll notice small white plugs around your engine bay that are attached to the frame using a single screw. They will have multiple wires running to them. These are the factory grounds and are a great place to ground the relay to. You’ll need a 10MM socket with an extension to get to it. Undo it, connect your ground and screw it back in securely.
The best place to run the long wire to the right side ballast is under the plastic cowling that runs along the front of the car directly under the hood. This way it’s completely out of the way of any moving parts and heat sources. Unfortunately it’s not quite long enough to come out the other side. This is where you’ll need the 9006 extension cord. Connect the extension and run it out the other side towards the right headlight.
The best place I found to mount the ballast was up inside the right fender. There is a slight flat spot high up and it mounts perfectly using 2 sided tape. The amp can mount to the inside of the body support also using 2 sided tape.
The last thing you need to do is run the ground for the right side ballast. Fortunately, you’ll find a factory ground point in the right side engine bay down under the air intake box. It's also a 10mm.
Now you can install the bulbs. Make sure and wipe them off carefully with the alcohol pads. They only fit in the housing one way.
You’re almost done! At this point you can hook up all the weatherpack connectors to the ballast and amps if you haven’t already done so and reinstall the battery. Make sure you have everything out of the engine bay, check your grounds and connections and fire em’ up!
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