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2007 Forester Sports XT 4EAT
156 Posts
Discussion Starter · #1 · (Edited)
On my 2007 FSXT, the low beam bulbs (H1) function as both low beams and also DRLs. Many other vehicles have their high beams as DRLs (run at a reduced brightness level), and I feel that this is safer because high beams are more noticable than low beams especially in the bright daytime. I was thinking of how to change the DRL system to allow the high beams to be run as DRLs, but couldn't seem to find anything online. So, I took a look at the schematics and came up with something that MIGHT work, but am not sure since I haven't tried it on my car yet. I was thinking if some of you could review the schematics and give me some feedback, that would be great!

First, I had to understand how the stock DRL system worked. Here is the original schematic:

The low beams' negatives are connected to the DRL relay and are normally routed to go through the resistor (thus providing a dimmer light for daytime use). When the light switch is turned to low beam (or position 2 according to the table), the coil of the DRL relay is energized, switching the path of the low beam to bypass the resistor straight to ground, providing full brightness.

On my automatic, the DRLs turn on only after the engine has started, the gear selector is out of Park, and the e-brake is released. QUESTION: for manual transmission cars, what conditions are required before the DRLs are on? There are two other sheets to the original lighting schematics located here: - PhotoPlog - Lighting Schematics sheets 2 & 3 but it's hard to tell how they affect the DRLs on the schematic. I am guessing that once all the conditions to activate DRLs are met, power to the low beams is activated (but the DRL relay coil remains de-energized, making use of the resistor).

Anyways, the first step was to remove the low beams from the DRL system -- basically performing a "disable DRL" mod. Before tackling using the high beams as DRLs, I thought it'd be easier if a totally different light source were to be used as DRLs (such as if you had an LED strip in the eyebrow). Here is what I came up with:

Alternate Lights as DRL

Note that red lines mean NEW wires/connections, and green lines mean REMOVED wires/connections. The magenta colored wires for the alternate light source assumes you've already wired your new lights to a positive source of your choice (more on this later).

To isolate the low beams from the DRLs, a new relay would be required (named "Low-Beam Relay" here). This could be your typical automotive relay (where the coils would be pins 85 & 86, the top pin would be 30, and pin 87 would be sent to ground). The new relay's coil would be wired in parallel to the DRL relay's coil, so that when the light switch is turned to position 2 (low beams on), the Low Beam Relay coil would energize, completing the low beam circuit to ground.

The DRL resistor would then need to be removed, and the pins on the wire harness would be shorted. The lights you want to run as DRLs would then be wired to the DRL relay at pin 1 -- but wire the NEGATIVES or GROUND SIDE to this pin. The positive would then go to a +12V source that is switched on when the car is running. I am not sure exactly how the ignition, gear selector, and ebrake status factor when the DRLs turn on, but I know that they do, so if you want your new lights to be just like the original DRLs, their positives will need to be wired to the same positive as the low beams.

Regarding Pin 5 (what happens when the DRL relay coil is energized due to the low beams turning on), it depends on what you want:

1. If you want the DRLs to TURN OFF when your low beams are turned ON, remove Pin 5 from ground, as shown.

2. If you want the DRLs to STAY ON when your low beams are turned ON, leave the connection to ground. Now, as long as the engine is on & gear is out of park (AT), the DRLs will stay on even if your low beams are turned on. This is probably ideal for those using LED strips.

Based on theory, this SHOULD remove your low beams as DRLs, and set a new light source to be your DRLs.

High Beams as DRL

These were a little bit trickier since I don't fully understand the original high beam circuit. It looks like the high beam circuit goes through the Hi-Beam Relay, but then goes through the light switch (in at pin 7, out at pin 16) before going to ground. This doesn't make sense to me because why would Subaru want all that current running through the switch? The reason for using a relay in the first place is to isolate main power from control. Maybe I'm not seeing something -- can anyone explain this?

Putting that aside and utilizing the theory in the previous schematic, here is what I came up with:

Basically everything is the same except for what goes into Pin 1 of the DRL Relay. In this case, we want the negative of the high beam bulbs to go into Pin 1, along with having the negative into the high beam relay as it is originally (so that the high beams still function when you pull/push the stick). To do this, connect Pin 1 of the DRL relay to Pin 1 of the Hi-Beam Relay. This should, in theory, allow the high beams to have two paths to ground: 1) through the high beam relay when you flash the high beams and 2) through the DRL relay.

In this case, you want to disconnect Pin 5 of the DRL Relay from ground, so that when you turn the low beams on, the high-beam-DRLs turn OFF (path to ground interrupted).

Additionally, so the high beam indiciator light doesn't stay lit all the time, it needs to be moved. Currently, it is wired in parallel to the high beam bulb so that whenever the high beam bulbs light up, the indicator light also lights up. I think by moving the negative of the indicator light past the hi-beam relay contact, it will only light up when the high beam switch is activated.

Again, I have NOT tested this mod, so I do not know if it works or not. Plus, I did not factor in the conditions required to activate the DRL -- this needs to be looked into. If any brave soul wants to try this out, please report back your success/failure!

I am not the first to come up with this -- DrMemory over at scoobymods mentioned he did something similar (ScoobyMods - View Single Post - Disabling DRL's - (Daytime Running Lights)) and to contact him for the schematics. However, that post was back in 2007, and I don't have enough posts over there to PM/Email him. Perhaps someone could try contacting him for the schematic? I'm curious as to how he did it, and the proposed simplicity for the rewiring to be completed in 20 minutes.
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