Here is a simple circuit you can build to add daytime running lights to a 94-01 Acura Integra. Keep in mind that this should be performed at your own risk and standard automotive electrical precautions should be followed while working on your vehicle. This build is a prototype and can be refined. I am simply writing this as a guide to add a feature that may not be equipped from the factory. Feel free to source your own parts and/or streamline the process to better suit your needs. Ok, here we go!
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Step 1: Parts.
I chose to source parts from Amazon.com that were relatively inexpensive. I used a fog lamp wiring harness similar to the picture and two 100 watt 2ohm resistors (same ones pictured). Total parts cost was $20.67 and some free time. I spent approx 2hrs on this project.
Step 2: Identifying the Circuit
Using the wiring diagram, I concluded that if I spliced into the red/blue striped wire with a lower voltage power source it would illuminate the high beam headlight bulbs enough to be visible but not at full brightness. This is where the resistors are key. But we will get into that a little later. At this location, the circuit is still protected by the factory fuse box and only one connection is needed to illuminate both bulbs. The wire we are using is very conveniently located on the bottom right side, back of the fuse box. There is a green connector you can disconnect for better accessibility and testing. You can verify that this is the correct wire by using a test light at the red/blue stripe terminal. If the test light will illuminate when the high beams are turned on at the switch, you have the correct wire.
Step 3: Identifying Power Sources
Another benefit on this fuse box is the empty terminals on the top. They are the perfect size for spade terminals for easy connection. We will use terminal #5 for a always hot B+ connection and #3 for a switched ignition B+ connection. You can also use a test light to verify that terminal #5 is "always hot" by testing the terminal with the key off. If the test light illuminates that terminal has battery power or is always hot. You can test terminal #3 with the test light as well. If the test light illuminates with the KEY ON, it is the switched ignition connection. The test light should go out when the key is turned off. I will explain where we will be making these connections a little later.
Step 4: Building the Resistor Assembly
Building the resistor assembly is pretty straightforward. I began with a piece of tin that I riveted the resistors to. You could use small screws if you like but I chose the rivets to keep the backside as flush as possible. Then I soldered the two resistors together in parallel (see picture) at both ends. Afterwards I soldered wire to the top left resistor and the bottom right resistor to place the resistor assembly in series with the power lead going to the red/blue stripe wire. These resistors will get very hot during use so I connected a 2" 12v dc computer fan to help cool things down. I had one laying around my spare parts drawer otherwise you may want to purchase one. The fan only draws 0.15 amps so I spliced into the wire going into the resistor assembly and provided an individual ground wire. I attached the assembly to the cruise control module on the drivers side kick panel with some double sided tape.
Step 5: Making the Connections
Now that we have a good idea of where to make our connections, we can start applying what we know of the circuits to make it work. I have labeled a diagram for the relay terminals to make it easier to identify. We will start with terminal #30 on the fog lamp relay and harness. Since the harness already has a connector and wiring we will simply run the wire to length from the terminal #30 slot to terminal #5 on the fuse box, attach a spade connector and connect it into terminal slot #5. One connection down, three to go. Next we will focus on the wire coming from the terminal #86 slot on the relay harness. We will run the wire to length to the #3 terminal slot on the fuse box, attach a spade connector and connect it into the #3 terminal slot. 2 connections made. Next we will make our ground connection. On terminal #85 of the relay harness we will run the wire to length to a 10mm bolt in the kick panel location (see picture), attach a ring terminal and use the bolt to attach our ground. As you can see in the picture, I used the same location for the fan ground as well. That's three connections, we're almost there! Last we will use terminal #87 on the fog lamp relay harness. We will run the wire to length to the resistor assembly we made and make the connection using a butt connector off the top left lead of the resistor assembly. Next we will attach a wire using a butt connector to the lower right lead of the resistor assembly, run the wire to length to the red/blue striped wire we identified earlier. We will cut the red/blue wire in two and strip both ends. On one end of the red/blue striped wire we will also strip the wire we ran from the resistor assembly and twist the two together. Install the butt connector on the twisted wires and crimp them. Then, install the butt connector to the other end of the red/blue striped wire and crimp it to complete the connection (see picture). I left the connection bare for the picture but be sure to wrap all of your connections with electrical tape! All done with the electrical connections!
Step 6: Mounting the Relay
Using the existing bolts in the kick panel area, I mounted the relay securely and out of the way. This is just a guideline, you can mount it wherever it may suit your needs or preferences. See picture for example.
Step 7: Checking for Operation
So now that we have everything installed and wired in correctly, we can check for operation. Because this system was designed to operate similarly to a factory DRL system, it will operate anytime the key is in the ignition on position. With the key in the ignition on position, the high beam headlights should operate dimly. With the headlight switch in the on position both the low beam headlights and DRL's should be illuminated simultaneously. Finally, when the high beam switch is turned on it bypasses the resistors and operates the headlamps at full brightness. This system design retains all of the functions of the high beam headlight system so it operates normally. It is a supplement built onto the factory system to add a modern safety feature to an older vehicle. See picture for example of operation.