DIY: Fog light to DRL conversion on V36 with A/T
#1
09-10-2014, 06:13 PM
DIY: Fog light to DRL conversion on V36 with A/T
I’ve been thinking about Daytime Running Lights (DRL) on my 2007 G35X sedan lately. I live in the northwest. With winter’s shorter days and the cloudy weather we’re famous for, DRL makes sense to me. However I think the aftermarket LED kits look so aftermarket. In Canada my model car uses what we in the US call the fog lights as the DRL. I perused the g35driver.com forums and found some DIY DRL fog light conversion ideas from others. One design turns the fog lights on when the ignition is on. Another design turns the fog lights on when the engine is running, controlled by the fuel pump power. Both designs use the parking light power to revert the DRL back to factory fog light behavior when the headlights are switched on. On my wife’s 2010 Subaru the factory DRL turns on when the engine is running and the A/T is not in the P position. I was hoping to emulate this behavior on my G35. This design idea is similar to the fuel pump power design but a bit different, so I thought I’d share it here. Please note that this design only works with the A/T car not the manual.
Like the other DIY DRL fog light conversion designs, the wiring modifications are made in the Intelligent Power Distribution Module (IPDM); which is found on the passenger fender wall next to the battery. This DRL conversion design uses two relays. One relay controls how the fog lights are powered and the other relay senses the A/T Park Neutral Position (PNP) switch signal to further control when the fog lights are powered. The PNP switch signal is used to power the IPDM starter relay coil and the starter control relay coil, so bleeding off another 40mA is no strain on the factory circuit.
I recommend reading the PCS (Power Control System) service manual, which if you haven’t downloaded the service manuals for your car, you should; there are plenty of threads on how to get them. In the PCS service manual study the IPDM E/R (Intelligent Power Distribution Module Engine Room) wiring diagram, terminal layout and physical values table. As a reference I’ve attached a PDF of the IPDM terminal layout and physical values table from the PCS service manual for the 2007 G35 sedan.
Also attached is a PDF of the DRL fog light conversion wiring diagram design that I came up with that works for a 2007/2008 G35 sedan with A/T. Wire colors maybe different for other year G35/G37s, but the concept should be the same. Study the PCS service manual for your model year to be certain.
The Pico relay (P/N 5593pt) was selected because it’s all sealed; both the relay and its connector/harness. It lives in the engine bay zip tied to the IPDM cable below the IPDM. This relay has a built-in resistor across the coil to help protect other circuit elements. The Radio Shack relay (P/N 275-031) is easy to get and small enough (1 inch x 1 inch) to mount inside the IPDM above the E9 connector using a small piece of surface mounting tape found in most auto parts stores. The diodes come as a two pack at Radio Shack (P/N 276-1102). The Radio Shack relay has PC board pins so I soldered one diode across the coil pins and 6 inch lengths of wire (18 AGW) to each of the relay pins, except the NO pin (Normally Open relay contact) , at the kitchen table before starting work on the car. I also cut one Pico relay coil wire and soldered the other diode in line at the cut then used adhesive shrink tubing to cover and seal the diode and solder connections. The 15A inline fuse is a waterproof sealed unit. It was soldered to the Pico relay 87 wire (Normally Open relay contact) and sealed with adhesive shrink tubing. A 5/16 inch eyelet terminal connector was crimped to the fuse power side wire and later bolted to the rear of the positive battery terminal, beneath the terminal’s plastic red cover.
The Radio Shack relay pin connection layout is printed on its packaging. The Pico relay didn’t have a similar diagram, so to help sort out which connector is which (or any other Bosch general purpose SPDT relay) refer to the bottom of the DRL wiring diagram PDF.
Per other DIY suggestions, the battery was removed (see DIY replacing your battery) to make more room to work on the IPDM. The IPDM has two clips found at the top on its fender side. Press these clips while lifting the IPDM straight up out of the fender well bracket. Next the IPDM has a clamshell cover which is held closed by two clips found at the cable end of the IPDM. With the IPDM cover off the terminals and wires are exposed. Only two wires were cut, the white and blue fog light wires found at IPDM connector E8, connector wires 86 and 87; refer to the IPDM E/R terminal layout drawing in the PCS service manual. All the other wiring connections were tee splices. A small section of the IPDM wire’s insulation was gently removed with an X-ACTO knife so as not to cut or nick the conductor wire. The tee wire was wrapped and soldered to the now bare IPDM wire section. Instead of using electrical tape, which is bulky and may unravel with time, liquid electrical tape was painted over the solder joints; found at the hardware store. I also painted the Radio Shack relay pin solder joints to protect them as well.
When do the fog lights lite up?
When the ignition is off, the fog lights function per factory; i.e. when the headlights are on low beam and the fog light switch is on, the fog lights are on.
When the ignition is on, without starting the car, the fog lights function per factory.
When the engine is started and running while A/T is in P or N position, the fog lights function per factory.
When the engine is running and the A/T in the D or R position and the headlight switch is off, the fog lights are on acting as daytime running lights.
When the engine is running and the A/T is the D or R position and the headlights or parking lights are switched on, the fog lights function per factory.
I want to thank the others on the g35driver.com forum for their DIY DRL fog light conversion ideas; they’ve helped me get to this design.
Like the other DIY DRL fog light conversion designs, the wiring modifications are made in the Intelligent Power Distribution Module (IPDM); which is found on the passenger fender wall next to the battery. This DRL conversion design uses two relays. One relay controls how the fog lights are powered and the other relay senses the A/T Park Neutral Position (PNP) switch signal to further control when the fog lights are powered. The PNP switch signal is used to power the IPDM starter relay coil and the starter control relay coil, so bleeding off another 40mA is no strain on the factory circuit.
I recommend reading the PCS (Power Control System) service manual, which if you haven’t downloaded the service manuals for your car, you should; there are plenty of threads on how to get them. In the PCS service manual study the IPDM E/R (Intelligent Power Distribution Module Engine Room) wiring diagram, terminal layout and physical values table. As a reference I’ve attached a PDF of the IPDM terminal layout and physical values table from the PCS service manual for the 2007 G35 sedan.
Also attached is a PDF of the DRL fog light conversion wiring diagram design that I came up with that works for a 2007/2008 G35 sedan with A/T. Wire colors maybe different for other year G35/G37s, but the concept should be the same. Study the PCS service manual for your model year to be certain.
The Pico relay (P/N 5593pt) was selected because it’s all sealed; both the relay and its connector/harness. It lives in the engine bay zip tied to the IPDM cable below the IPDM. This relay has a built-in resistor across the coil to help protect other circuit elements. The Radio Shack relay (P/N 275-031) is easy to get and small enough (1 inch x 1 inch) to mount inside the IPDM above the E9 connector using a small piece of surface mounting tape found in most auto parts stores. The diodes come as a two pack at Radio Shack (P/N 276-1102). The Radio Shack relay has PC board pins so I soldered one diode across the coil pins and 6 inch lengths of wire (18 AGW) to each of the relay pins, except the NO pin (Normally Open relay contact) , at the kitchen table before starting work on the car. I also cut one Pico relay coil wire and soldered the other diode in line at the cut then used adhesive shrink tubing to cover and seal the diode and solder connections. The 15A inline fuse is a waterproof sealed unit. It was soldered to the Pico relay 87 wire (Normally Open relay contact) and sealed with adhesive shrink tubing. A 5/16 inch eyelet terminal connector was crimped to the fuse power side wire and later bolted to the rear of the positive battery terminal, beneath the terminal’s plastic red cover.
The Radio Shack relay pin connection layout is printed on its packaging. The Pico relay didn’t have a similar diagram, so to help sort out which connector is which (or any other Bosch general purpose SPDT relay) refer to the bottom of the DRL wiring diagram PDF.
Per other DIY suggestions, the battery was removed (see DIY replacing your battery) to make more room to work on the IPDM. The IPDM has two clips found at the top on its fender side. Press these clips while lifting the IPDM straight up out of the fender well bracket. Next the IPDM has a clamshell cover which is held closed by two clips found at the cable end of the IPDM. With the IPDM cover off the terminals and wires are exposed. Only two wires were cut, the white and blue fog light wires found at IPDM connector E8, connector wires 86 and 87; refer to the IPDM E/R terminal layout drawing in the PCS service manual. All the other wiring connections were tee splices. A small section of the IPDM wire’s insulation was gently removed with an X-ACTO knife so as not to cut or nick the conductor wire. The tee wire was wrapped and soldered to the now bare IPDM wire section. Instead of using electrical tape, which is bulky and may unravel with time, liquid electrical tape was painted over the solder joints; found at the hardware store. I also painted the Radio Shack relay pin solder joints to protect them as well.
When do the fog lights lite up?
When the ignition is off, the fog lights function per factory; i.e. when the headlights are on low beam and the fog light switch is on, the fog lights are on.
When the ignition is on, without starting the car, the fog lights function per factory.
When the engine is started and running while A/T is in P or N position, the fog lights function per factory.
When the engine is running and the A/T in the D or R position and the headlight switch is off, the fog lights are on acting as daytime running lights.
When the engine is running and the A/T is the D or R position and the headlights or parking lights are switched on, the fog lights function per factory.
I want to thank the others on the g35driver.com forum for their DIY DRL fog light conversion ideas; they’ve helped me get to this design.
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joedaddy1 (09-11-2014)
#4
09-12-2014, 06:21 PM
I worked on this design for a few days, going over various ideas before settling on this one. Because I’m familiar with the circuit, maybe I left out some information that would help someone else take on this mod. It’s really not that scary to do. But you should have a basic understanding of how the different components in this design work and some basic soldering experience. You can watch soldering techniques on YouTube and practice at your kitchen table; if your significant other allows it that is.
Bear with me if this is too simplistic; I have to start somewhere. Refer to the DRL wiring diagram PDF at the beginning of this thread to follow along as I detail how this mod works. The SPDT (Single Pole Double Throw) relay has five connectors total. It consist of a coil (connectors 85 & 86), 1 common connector (30), 1 normally closed connector (87a), and 1 normally open connector (87). The numbers are a standard used on a Bosch style general purpose SPDT relay. The bottom of the PDF shows the numbers relationship to relay’s physicality. A relay uses an electromagnet to mechanically operate a switch. A low power signal flows current through the relay coil that energizes the electromagnet to operate the switch, which can control much higher power. If there’s no voltage across the relay coil connectors, the common connector is switched to the normally closed connector. If there is a voltage across the relay coil connectors, the electromagnet moves the switch so the common connector is now switched to the normally open connector. Start with the Pico relay (a Bosch SPDT type of relay) in the diagram. This relay requires only 136mA of coil current to operate the relay’s switch. The relay switch itself is capable of switching up to 30A, which is twice what the 15A fuse rating is. Perfect for our fog lights (55 Watt bulbs) which use just under 10A total, being wired together. The Radio Shack relay is smaller, both physically (nice because it fits inside the IPDM) and in its power ratings. This relay requires only 37mA of coil current to operate the relay’s switch (nice because it won’t tax the factory PNP switch signal). The relay’s switch will only be loaded with the current from the Pico relay’s coil, 136mA, which is way below this relay’s switch rating of 10A. If you’re not familiar with a diode, think of it as a one way valve which allows current to flow in one direction but not the other. See the triangle in the diode’s symbol in the wiring diagram as an arrow showing which way the diode allows current to flow. On a diode you’ll see a small stripe or ring painted at one end of it. Be sure the striped end of the diode is orientated as shown in the DRL wiring diagram PDF when you’re soldering the components together; the bar at the end of the triangle matches the striped end of the diode.
How this mod operates.
When the ignition switch is off, the fuel pump power is off, so there’s no voltage across the Pico relay’s coil and the Pico relay’s switch is in the normally closed position, connecting the fog lights (30) to the factory fog light power (87A); the fog light s function per factory. Also with the ignition switch off, there is no signal from the PNP switch, so no matter what position the A/T is in there’s no voltage across the Radio Shack relay coil. The Radio Shack relay’s switch is in its normally closed position, connecting the Pico relay coil (85) to the Radio Shack’s normally closed connector, which is wired to the parking light. When the parking lights are off there is a path to ground through the parking light bulb filament. If you switch on the headlights, that will power on the parking lights putting 12V at one end of the Pico relay coil (85). The other side the Pico relay coil (86) has a diode connected to it. Because of the diode’s orientation, current won’t flow through the Pico relay coil, so the Pico relay’s switch still connects the fog lights (30) to the factory fog light power (87A); the fog lights function per factory.
The engine is running and the A/T is in P or N position. Because the engine is running, there’s power coming from the fuel pump power supply putting 12V at one end of the Pico relay coil (86). Because the A/T is in P or N position, there’s 12V across the Radio Shack relay coil, so the Radio Shack relay’s switches to its normally open position; connecting its common connector, wired to the other side of the Pico relay coil (85), to the Radio Shack’s normally open connector, which has nothing wired to it. Despite there being 12V at one end of the Pico relay coil (86), the other side of the Pico relay coil (85) has nothing connected to it, so no current flows through the Pico relay coil and the Pico relay’s switch is in its normally closed position, connecting the fog lights (30) to the factory fog light power (87A); the fog lights function per factory.
The engine is running, the A/T is in the R or D position and the headlight switch is off. As above, there’s power coming from the fuel pump power so there’s 12V at one end of the Pico relay coil (86). With the A/T is in the R or D position, there’s no voltage across the Radio Shack relay coil, so the Radio Shack relay’s switch is in its normally closed position, connecting its common connector, wired to Pico relay coil (85), to the Radio Shack’s normally closed connector, which is wired to a parking light. Because the headlight switch is off there is a path to ground through the parking light bulb filament. This means there’s 12V across the Pico relay’s coil. The 136mA of current flowing through the Pico coil energizes the Pico relay’s electromagnetic switch, but it’s not enough current to cause the parking light bulb to lite up. Now the Pico relay’s switch connects the fog lights (30) to the battery power (87); the fog lights are on, functioning as daytime running lights. Let’s turn on the headlights. Now there’s 12V on the parking light bulb. That means there’s 12V on both sides of the Pico relay coil, the fuel pump power supply (86) and the parking light (85). Because there’s no voltage drop across the Pico relay coil, the Pico relay’s switch switches to its normally closed position, connecting the fog lights (30) to the factory fog light power (87A); the fog lights function per factory.
There’s one case I didn’t detail because it’s a bit more complicated. When the ignition switch is turned on, but the engine is not started; that is you pressed the ignition button without pressing your foot on the brake pedal. You’ll note in the DRL wiring diagram that the fuel pump power supply turns on for a short while when the ignition switch is on. The factory circuit does this to add fuel pressure to the fuel injectors, priming them with fuel for an engine start. Because an engine start wasn’t commanded, after about 1 second the factory circuit turns off the fuel pump power. With the A/T is in the P or N position when the ignition switch is turned on, the PNP switch signal is 12V causing the Radio Shack relay coil to energize so the Radio Shack relay’s switches the common connector to the normally open connector, which isn’t wired to anything. So for that brief second there’s 12V at one end of the Pico relay coil (86), but the other side of the Pico relay coil (85) has nothing connected to it. The Pico relay switch stays in its normally closed position, connecting the fog lights (30) to the factory fog light power (87A). In my original post I mentioned that I borrowed from a fuel pump power design, similar to this one. Because that other design wasn’t using the PNP switch signal to control a second relay, it had a one second flash on of the fog lights when the ignition was turned on, but the engine wasn’t started. This design doesn’t have that issue.
The last component to detail is the diode across the Radio Shack relay coil. This diode is there to protect the factory circuit that the relay coil connects to from a condition called a back EMF spike. When a diode is wired across a relay coil like this it’s called a flywheel diode; some called it a flyback diode. There’s a magnetic field produced by the current flowing through the coil that controls the electromagnet switch in the relay. The magnetic field is like a flywheel, its stored energy. When the voltage is removed from the coil there’s a very short lived voltage spike that can potentially harm sensitive solid state circuit elements that maybe part of the factory circuit. The flywheel diode provides a discharge path for the remnant stored energy in the coil. The Pico relay has a built in resistor across its coil to perform a similar function.
Too much info or the more arrows in your quiver the better you are with DIYs?
Bear with me if this is too simplistic; I have to start somewhere. Refer to the DRL wiring diagram PDF at the beginning of this thread to follow along as I detail how this mod works. The SPDT (Single Pole Double Throw) relay has five connectors total. It consist of a coil (connectors 85 & 86), 1 common connector (30), 1 normally closed connector (87a), and 1 normally open connector (87). The numbers are a standard used on a Bosch style general purpose SPDT relay. The bottom of the PDF shows the numbers relationship to relay’s physicality. A relay uses an electromagnet to mechanically operate a switch. A low power signal flows current through the relay coil that energizes the electromagnet to operate the switch, which can control much higher power. If there’s no voltage across the relay coil connectors, the common connector is switched to the normally closed connector. If there is a voltage across the relay coil connectors, the electromagnet moves the switch so the common connector is now switched to the normally open connector. Start with the Pico relay (a Bosch SPDT type of relay) in the diagram. This relay requires only 136mA of coil current to operate the relay’s switch. The relay switch itself is capable of switching up to 30A, which is twice what the 15A fuse rating is. Perfect for our fog lights (55 Watt bulbs) which use just under 10A total, being wired together. The Radio Shack relay is smaller, both physically (nice because it fits inside the IPDM) and in its power ratings. This relay requires only 37mA of coil current to operate the relay’s switch (nice because it won’t tax the factory PNP switch signal). The relay’s switch will only be loaded with the current from the Pico relay’s coil, 136mA, which is way below this relay’s switch rating of 10A. If you’re not familiar with a diode, think of it as a one way valve which allows current to flow in one direction but not the other. See the triangle in the diode’s symbol in the wiring diagram as an arrow showing which way the diode allows current to flow. On a diode you’ll see a small stripe or ring painted at one end of it. Be sure the striped end of the diode is orientated as shown in the DRL wiring diagram PDF when you’re soldering the components together; the bar at the end of the triangle matches the striped end of the diode.
How this mod operates.
When the ignition switch is off, the fuel pump power is off, so there’s no voltage across the Pico relay’s coil and the Pico relay’s switch is in the normally closed position, connecting the fog lights (30) to the factory fog light power (87A); the fog light s function per factory. Also with the ignition switch off, there is no signal from the PNP switch, so no matter what position the A/T is in there’s no voltage across the Radio Shack relay coil. The Radio Shack relay’s switch is in its normally closed position, connecting the Pico relay coil (85) to the Radio Shack’s normally closed connector, which is wired to the parking light. When the parking lights are off there is a path to ground through the parking light bulb filament. If you switch on the headlights, that will power on the parking lights putting 12V at one end of the Pico relay coil (85). The other side the Pico relay coil (86) has a diode connected to it. Because of the diode’s orientation, current won’t flow through the Pico relay coil, so the Pico relay’s switch still connects the fog lights (30) to the factory fog light power (87A); the fog lights function per factory.
The engine is running and the A/T is in P or N position. Because the engine is running, there’s power coming from the fuel pump power supply putting 12V at one end of the Pico relay coil (86). Because the A/T is in P or N position, there’s 12V across the Radio Shack relay coil, so the Radio Shack relay’s switches to its normally open position; connecting its common connector, wired to the other side of the Pico relay coil (85), to the Radio Shack’s normally open connector, which has nothing wired to it. Despite there being 12V at one end of the Pico relay coil (86), the other side of the Pico relay coil (85) has nothing connected to it, so no current flows through the Pico relay coil and the Pico relay’s switch is in its normally closed position, connecting the fog lights (30) to the factory fog light power (87A); the fog lights function per factory.
The engine is running, the A/T is in the R or D position and the headlight switch is off. As above, there’s power coming from the fuel pump power so there’s 12V at one end of the Pico relay coil (86). With the A/T is in the R or D position, there’s no voltage across the Radio Shack relay coil, so the Radio Shack relay’s switch is in its normally closed position, connecting its common connector, wired to Pico relay coil (85), to the Radio Shack’s normally closed connector, which is wired to a parking light. Because the headlight switch is off there is a path to ground through the parking light bulb filament. This means there’s 12V across the Pico relay’s coil. The 136mA of current flowing through the Pico coil energizes the Pico relay’s electromagnetic switch, but it’s not enough current to cause the parking light bulb to lite up. Now the Pico relay’s switch connects the fog lights (30) to the battery power (87); the fog lights are on, functioning as daytime running lights. Let’s turn on the headlights. Now there’s 12V on the parking light bulb. That means there’s 12V on both sides of the Pico relay coil, the fuel pump power supply (86) and the parking light (85). Because there’s no voltage drop across the Pico relay coil, the Pico relay’s switch switches to its normally closed position, connecting the fog lights (30) to the factory fog light power (87A); the fog lights function per factory.
There’s one case I didn’t detail because it’s a bit more complicated. When the ignition switch is turned on, but the engine is not started; that is you pressed the ignition button without pressing your foot on the brake pedal. You’ll note in the DRL wiring diagram that the fuel pump power supply turns on for a short while when the ignition switch is on. The factory circuit does this to add fuel pressure to the fuel injectors, priming them with fuel for an engine start. Because an engine start wasn’t commanded, after about 1 second the factory circuit turns off the fuel pump power. With the A/T is in the P or N position when the ignition switch is turned on, the PNP switch signal is 12V causing the Radio Shack relay coil to energize so the Radio Shack relay’s switches the common connector to the normally open connector, which isn’t wired to anything. So for that brief second there’s 12V at one end of the Pico relay coil (86), but the other side of the Pico relay coil (85) has nothing connected to it. The Pico relay switch stays in its normally closed position, connecting the fog lights (30) to the factory fog light power (87A). In my original post I mentioned that I borrowed from a fuel pump power design, similar to this one. Because that other design wasn’t using the PNP switch signal to control a second relay, it had a one second flash on of the fog lights when the ignition was turned on, but the engine wasn’t started. This design doesn’t have that issue.
The last component to detail is the diode across the Radio Shack relay coil. This diode is there to protect the factory circuit that the relay coil connects to from a condition called a back EMF spike. When a diode is wired across a relay coil like this it’s called a flywheel diode; some called it a flyback diode. There’s a magnetic field produced by the current flowing through the coil that controls the electromagnet switch in the relay. The magnetic field is like a flywheel, its stored energy. When the voltage is removed from the coil there’s a very short lived voltage spike that can potentially harm sensitive solid state circuit elements that maybe part of the factory circuit. The flywheel diode provides a discharge path for the remnant stored energy in the coil. The Pico relay has a built in resistor across its coil to perform a similar function.
Too much info or the more arrows in your quiver the better you are with DIYs?
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