The RetrofitSource Xenon Installation Guide on 2015 Prius

Hi everyone,

Long time lurker, first time poster. I recently became the proud owner of a 2015 Prius Three. The most practical car I've owned by far. One upgrade that I always planned on doing as soon as I decided on the Prius was to change out the stock halogen bulbs to xenon bulbs, especially given the excellent stock projector setup on the Prius. I scoured this forum and several others and found many helpful pictures and posts, but the information was spread out across many different threads and posts. So I collected all the relevant pieces of information to make a unified, singular xenon installation guide that I hope will be helpful to anyone else who is thinking of doing this upgrade. Here it is:

DISCLAIMER
This guide is meant for educational purposes only. I am not an automotive mechanic or engineer by trade or training. The contents of this guide are based solely on my personal experience and should not be interpreted as an authoritative or expert opinion. Before proceeding, you must understand that your decision to follow this guide and/or perform work on your car is done at your own risk. I will not and cannot be held responsible for any damage to person and/or property incurred by your attempt to follow the information outlined below. I will not and cannot be held responsible for any unforeseen circumstances and/or limitations in your technical and/or general knowledge you may encounter upon attempting to follow this guide. Please proceed at your own risk in acting upon the information outlined below.

Also, I acknowledge that some pictures I use below for illustrative purposes are not my own. Full credit is given to their original authors.

Equipment
After doing my share of research about the various kits out there, I chose the H11 Morimoto Elite HID System from The RetrofitSource (TRS). Morimotos have an excellent track record in terms of performance and quality, and the RetrofitSource also has an excellent reputation for great customer service and standing behind their products. I wanted these lights to serve a functional purpose and last me in the long run, so I thought the extra money for the Morimoto kit was worth it. And as expected, TRS was great to work with and were very responsive to any questions I had both before and after I received the package in the mail.

Specifically, I paired the 35W ballast with the XB35 4500K bulbs. Many people on the forum have successfully used the 55W ballast for increased light output, but I chose the 35W ballast to get a little more lifespan out of my bulbs, even at the cost of relatively diminished output.

I also ran a relay to my bulbs. Many people on the forum have successfully connected their bulbs directly into the OEM wiring without any issues. Admittedly, running a relay will add a significant amount of extra work and time to the installation process. Again, this is just a personal preference/paranoia of mine in doing whatever I could to ensure longevity of the bulbs and not running into any issues later on down the road.

Required Tools
- 10mm socket wrench: will need to loosen the bolts holding coolant tank (I tried to do this with a regular hand wrench and found it quite difficult. The stock bolts are secured very tightly, so you definitely need some extra torque to loosen the bolts)
- Zip Ties: will need to tidy up/secure wires
- Wire Cutters: will need to cut extra slack on zip ties
- 3M Mounting Tape: will need to secure ballasts to body panel
- Alcohol wipe: will need to clean any oil residue transferred from your fingers onto the bulbs

Required Time
I've done some very basic work on cars (changed bulbs, wipers, etc) but by no means have extensive mechanical experience. It took me about 3-4 hours to do this install from start to finish. A lot of that time, however, was spent on making small adjustments/finishing touches. I also worked very slowly and deliberately to make sure I didn't miss a step. If I were to do it again, knowing what I know now, it would probably take me half the time. Hopefully, this guide will help you work through things a bit faster than I did. However, I would definitely leave plenty of time for yourself to do this installation, especially if it's your first major modification to your car.

TRS Package Contents

I forgot to take a picture of everything before installation, so I only have this picture post-installation. The bulbs were in a box in the top left corner, followed by a box for each of the ballasts. The wires that connect into each of the bulbs were packaged in individual bags. The relay itself was in a separate bag. All the contents were brand-new and in great shape. All the wiring was encased in a durable fabric sheath (made of bungee-cord material) for extra durability, as you can see in pictures below.

Installation Guide

1. Open hood

2. Driver’s side

a. Disconnect factory harness from bulb

b. Rotate bulb counter-clockwise and pull out

c. Switch rubber grommet from OEM bulb to HID bulb. This will avoid the problem some have encountered with finding it difficult to push in and seat the new bulb due to the stiff rubber of the non-OEM grommet. Ensure the grommet is seated at the base of the plastic bulb holder as illustrated below.


Be sure to seat the grommet against the base of the bulb holder (Picture from prior PriusChat thread)


d. Ensure that largest of three tabs is facing opposite (12 o’clock) of ground wire (6 o’clock) when locked in. The Morimoto bulbs from TRS already come seated in their socket, so there’s no need to scrutinize this step.

e. Clean bulb with an alcohol wipe to clean any oils from your fingers that may have transferred onto the bulbs

f. GENTLY insert bulb (held at the 10 o’clock orientation) back into projector. Once seated, twist clockwise from 10 o’clock orientation to 12 o’clock orientation to secure in place. Do not force the bulb in at any point. Doing so will risk breaking the bulb.


3. Passenger side

a. Use 10 mm socket wrench to disconnect two nuts holding in coolant tank

b. Move coolant tank to the side

c. Disconnect factory harness from bulb

d. Rotate bulb counter-clockwise and pull out

e. Switch rubber gasket from OEM bulb to HID bulb

f. Ensure that largest of three tabs is facing opposite (12 o’clock) of ground wire (6 o’clock when locked in). The Morimoto bulbs from TRS already come seated in their socket, so there’s no need to scrutinize this step.

g. Clean bulb with an alcohol wipe to clean any oils from your fingers that may have transferred onto the bulbs

h. GENTLY insert bulb (held at the 10 o’clock orientation) back into projector. Once seated, twist clockwise from 10 o’clock orientation to 12 o’clock orientation to secure in place. Do not force the bulb in at any point. Doing so will risk breaking the bulb.

i. Only driver’s side OEM harness will connect to relay. Passenger side OEM harness remains empty. Tape it to keep water out

4. Relay Wiring



General wiring layout of relay wiring (Graphic from TRS). My TRS kit had all the individual wires from the relay labeled.


Another wiring schematic I found on another forum

a. Connect the OEM harness on the DRIVER’S SIDE to the respective input on the relay wiring (“headlight plug” labeled in the image below)


Real-life picture of the relay harness. Notice the asymmetry of the wire lengths, with the longer ballast connection and ground wire intended to reach the passenger side (Picture from prior PriusChat thread)


Another view of how the relay wiring should connect to the ballasts and bulbs (Picture from another forum)

b. Secure the ground wires on both the passenger side and driver’s side. Ground to the 10 mm bolt on the chassis on each side. Make sure ground wire is contacting bare metal (i.e. not plastic). Sand/clean metal contact as necessary. Here are some potential grounding sites:

i. Driver’s Side


A possible chassis grounding point on the driver side (Picture from prior PriusChat thread)


ii. Passenger’s side


A possible chassis grounding point on the passenger side (Picture from prior PriusChat thread)


c. Tapping into the 12V power source in the fuse box

i. Open the fuse box cover by depressing two tabs on the side of the fuse box closest to the driver’s compartment. I couldn’t find a good video of this or figure out a better way to word this. If anyone else has a better description or illustration, please chime in.


Picture of the fuse box interior with the cover removed (Picture from prior PriusChat thread)


ii. Remove the small cover over the power terminal by pressing the two black tabs towards each other (use a thin flat head screw driver, such as one found in an eyeglass repair kit) and then pulling up to remove the smaller cover over the power terminal by bringing the two black tabs towards each other.


View of the fuse box with the 12V positive power source cover removed (Picture from prior PriusChat thread)


iii. Unscrew the 10 mm bolt, then secure the positive power source by tightening the 10 mm bolt on top of the positive power source ring

iv. Picture above indicates that you can also tuck away the fuse into the fuse box, but I did not have enough slack to do this


d. Securing the relay

i. Before securing the relay harness itself to the chassis (on the driver’s side), I found it useful to cut away some of the rubber sleeve that wraps around all the wires that feed into the harness. This helped generate more slack for the harness output that had to be run to the passenger side. With the rubber sleeve in place, there wasn’t enough slack to hide the passenger side harness wiring underneath the underside of the engine compartment.


ii. I used a 6mm x 16mm bolt to secure the relay to a hole in the chassis found near the inverter. I initially had some trouble getting the bolt to engage the hole in the relay and ended up having to dilate the hole in the relay with the shaft of the screw driver to allow the bolt to engage the hole in the relay. Considering this, I would recommend maybe using a screw rather than a bolt, since the sharp end of screw may help engage the hole in the relay. If you do decide to bolt the relay harness down in this location (some have used zip ties to secure the relay harness in other locations), this is another point in which a socket wrench will come in handy, both to reach this deep into the engine compartment and to generate sufficient torque.




An open threaded bolt hole on the driver side where you can consider bolting the relay harness (Picture from prior PriusChat thread)


Relay harness bolted into the aforementioned bolt hole (fuse box is on the right side of this picture)


A closer shot of where/how I mounted my relay (edge of fusebox is on the bottom of the picture)

iii. Some people just used zip ties to secure the relay harness


5. Ballast Connections


Photo courtesy of TRS

a. Insert the bulb inputs into the amp igniter on both the driver and passenger sides

b. Insert the ballast output from the amp igniter into the ballast

c. Insert the harness output into the ballast input

d. Check all connections above to make sure they are secure and correct


6. Light Test

a. At this point, all your connections should be made. All that remains is to organize and cleanup the wiring. It’s worthwhile to test the wiring now before tucking away the wiring for good.

b. Turn on the headlights and make sure both bulbs illuminate and no error lights are produced on the dashboard



7. Mounting ballasts

a. Place 3M double-sided tape on back of ballast. I purchased a 1 inch roll and cut it to size. Clean the back of the ballast with alcohol wipe before applying tape.

b. Driver side: remove the insulation panel to mount ballast as seen in the xenonsupply video

i. Remove cover of fuse box

ii. Remove two pins holding in black plastic panel using a flat head screw driver

iii. Clean rear side of plastic panel and ballast

iv. Mount 3M tape

v. Mount ballast in a way to ensure wiring can come out of bottom front portion of black panel

vi. Feed wires to the front around fuse panel


c. Passenger side: remove insulation panel to mount ballast as seen in xenonsupply video

i. You can follow the same steps as above. However, for me, after mounting the ballast behind the insulation panel, there wasn’t enough slack for the ballast connection from the driver side relay to securely plug into the ballast. This was despite freeing up some slack by cutting away the rubber sleeve that organized the wires feeding into the relay. As a result, I had to modify the mounting location of my passenger side ballast to adjust for this. I ended up wedging the passenger side ballast into the bottom edge of the insulation panel.



8. Organizing wires and running ballast connection to the passenger side

a. Use zip ties to organize/clean up the driver side wires by securing them to each other and/or to existing wires in the engine compartment


b. Use zip ties to secure the passenger side ballast wire and ground wire as it runs along the underside of the front of the engine compartment



Helpful Video Links: I personally found these videos very helpful for visualizing the installation process as well as how all the components fit together.

Step-by-step Morimoto HID installation on 2011 Sienna: similar steps using similar components as this tutorial

Xenonsupply.com Prius tutorial: non-TRS kit, but similar installation steps

Shorter xenonsupply.com Prius tutorial

Xenonsupply.com relay tutorial

2011 Prius HID installation: non-TRS kit but similar installation steps

Basics of relay wiring as demonstrated in a Mazda 3

Explanation of relay components

Relay installation on a non-TRS kit

 

Thanks for everyone's feedback! I'm glad that I could give something back after having learned so much from the forum.

@xliderider: thank you for your photographic contribution!

@kronos89: what kind of night shots are you referring to (inside looking out or just from the outside)? I do not have any night shots per se, but the visibility is much improved, as I'm sure you could attest to from upgrading your tacoma. There were several prior HID installation posts (this one, for example) on priuschat that included night-time shots. However, if you are looking for a specific angle/perspective, I can try to get it for you.