WHT Z06 Mods:
LED DRL and Tail Lights

I've done two C6 Corvette LED conversion projects, tail lights in 2009 and daytime running lamps (DRL) in 2017.


Tail Lights

I've always thought the C6 should have been made with LED tail lights. Not only do they look cool but there's a subtle safety aspect to them. They turn on much faster. Incandescent bulbs require 200 ms to come up to brightness. Eliminating this delay means the driver following you can react to your brake lights 200 ms sooner. When you're doing 55 MPH, that's sixteen feet!

[Blinking tail light]

There are a number of aftermarket C6 conversions out there but most of them look cheap to me. With a price range of $500 to $2100 they are are anything but. What I really wanted was factory appearance with LED internals.

[Pratt & Miller]

I learned that Pratt & Miller uses LED tail in their C6R race and C6RS street cars; further investigation revealed they use LED tail light modules first seen on the 2006 Mercury Mountaineer. These are glued into the stock C6 Corvette tail light reflector assemblies.

[Sylvania] [OSRAM]

The LED modules are made by Sylvania/OSRAM and are part of their Joule LED lighting system. This clever design places surface mount LEDs in a heat sink assembly outside of the tail light assembly. A clear plastic tube carries the light up to a mirror that shines it on the tail light reflector. Keeping the LEDs outside of the tail light is an important feature because LED light output is sensitive to ambient temperature.

There are currently two Joule LED module part numbers in use. The 2006 Mercury Mountaineer uses L1224R-01 and the 2008 Chevrolet Malibu LTZ uses L1230R-02 (GM 25874489). The focal lengths are encoded in the part number and are 24 and 30 mm while the focal length of the incandescent light socket in the C6 Corvette tail light is 29.45 mm. In an attempt to maintain the correct focal length, I used L1230R-02 modules. A drawback to this choice is that the L1230R-02 uses a 4-pin USCAR connector which is difficult to obtain.

Mounting

I wanted this modification to be reversible so gluing the modules in wasn't an option. I first considered making an adapater that the LED module would lock into and in turn lock into the tail light assembly. However, the geometry of the LED module's locking lugs and those on the C6 tail light socket make this design difficult to fabricate. Also, two weather seals instead of one would be needed and this would impact the focal length.

My solution was to make adapters that would mate with the C6 tail light and epoxy them to the LED modules. To make the mold master, I cut up a spare C6 tail light socket and glued a spacer to it. Next I made a mold using Alumilite QuickSet RTV silicone and cast a number of adapters using Alumilite Regular urethane resin.

Mold making preparation

The end product is surprisingly durable and can resist temperatures up to 250° F. It takes 4-8 hours for the silicone to cure but only 4-8 minutes for the resin to set so once the mold was completed it only I was able to quickly make all of the parts. Once the adapters were ready all that was left was to trim the lugs off the LED modules and epoxy the parts together with J-B Weld.

Final module assembly Locked into tail light

I notched the adapter to make it easy to maintain connector orientation when gluing. After applying a little dielectric grease, I reused the weather seals from the incandescent light sockets.

Load Resistors

A common problem with LED conversions is that the turn signal and emergency flashers blink too fast. A flasher is basically a coil wrapped around a bimetalic strip. When you apply current the coil heats the strip causing it to flex and break the circuit. As the strip cools, it straightens and completes the circuit.

LEDs draw less current than the incandescent bulbs they replace. This means the bimetalic strip doesn't heat up as much. Since it takes less time to cool down the flasher cycles faster. Adding resistors simulates the load of the incandescent lamp and causes the flasher to cycle at the original rate.

The C6 Corvette uses a 3057LL double filament wedge lamp in all four of the rear tail light assemblies. The primary filament is rated at 2.1 A @ 12.8 V. The pair on each side are wired in parallel when you do not have RPO T79. The LED modules are rated at 3.5 W @ 13.5 V which is 259 mA. If we add up the current from the two incandescent bulbs and subtract the current from the two LED modules we find that we'd like each load resistor to draw about 3.7 A @ 12.8 V. This means we can use 3.5 Ω, 50 W power resistors.

Wiring harness

Rather than hack up my wiring harness, I made a short adapter and inserted it at connector C455 which is located behind the right tail lamp assembly. This is the junction that connects the I/P harness to the deck lid harness and it provided access to all of the relevant tail light circuits; here's the pinout of connector (Rear body harness to I/P harness).

Pin Wire color Function
A BK Ground
B L-BU Stop lamp supply voltage
C L-GN Backup lamp supply voltage
D YE Left rear stop/turn lamp supply voltage
E BN Park lamp supply voltage
F TN Rear compartment lock actuator unlock
G D-GN Right rear stop/turn lamp supply voltage
H OG Rear fog lamp supply voltage (T79)

Note that RPO T79 is the export option for rear tail fog lights and so pin H is not used for domestic applications.

I attached the load resistors to a piece of 1/8" alumimum and mounted that under a ground on the right side bumper. I used a 3-pin Delphi connector to make it possible to disconnect the resistors and use the incandescent bulbs without having to remove my wiring harness.

[LED Tail Light]

The resistors are wired between ground (pin A) and the left (pin D) and right (pin G) tail/stop and turn signal circuits.

The 8-pin Delphi connectors are readily available but the 4-pin USCAR connectors are not. In the end I lucked out and found someone who had four. As more cars use these modules the connectors should become a commodity item. After I finished splicing the wires together I wrapped it in Elliott Tape ET-301 dry vinyl wiring harness tape which gave it a totally factory appearance.

[LED Tail Light]

Here's a parts list for the wiring harness:

Quanity Delphi Mouser Description
1 15326840 829-15326840 GT 150 8-way connetor (male)
1 15326835 829-15326835 GT 150 8-way connetor (female)
1 15326813 829-15326813 GT 150 3-way connetor (male)
1 13519047 829-13519047 GT 150 3-way connetor (female)
10 15326269 829-15326269 GT 150 terminal (male)
10 12191819 829-12191819 GT 150 terminal (female)
20 15366060 829-15366060 GT 150 cable seal (blue)
2 15305171 829-15305171 GT 150 cavity plug (green)
2   71-RH50-3.5 Power Resistors 50 W 3.5 Ω 1%

Notes


Daytime Running Lamps

The stock C6 Corvette daytime running and turn signal lamps are also incandecent so of course I wanted to ugprade them to LED.

[Blinking drl light]

Sylvania has two lines of automotive LED lamps. The first is the 4157A (4157ASL.BP2) which is a cylinder with 18 surface mount LEDs. These approximate the stock lamp output but I found the dim (marker light) brightness to appear dimmer than a stock 4157NA lamp.

Sylvania 4157A

The other option is the Sylvania Zevo 4157A (4157ALED.BP2). The dim circuit is perfect and the bright is brighter but only when looking from directly inline and looks good off-angle. These are what I used.

Sylvania Zevo 4157A Installed in DRL connector

Load Resistors

The stock DRL/turn signal lamp on a C6 Corvette is the 4157NA. There are two elements and the primary is rated 2.2 A @ 12.8 V, uses 28.5 W and outputs 302 lumens. Using a 6 Ω, 50 W power resistor gives us 25.6 W. The Sylvania Zevo is rated at 1.5 W @ 13.8 V which gives us 27.1 W.

Wiring harness

As with the tail lights mod I made two wiring harnesses to add a load resistor to each side. There is one connector for each side. C119 is the left and C120 is the right but the pinout is basically the same.

Pin Wire color Function
A BK Ground
B YE Headlamp Low Beam
C D-GN/WH Headlamp High Beam Supply Voltage
D L-BU/WH Front Turn Signal Lamp Supply Voltage
E BN Park lamp supply voltage

All of the circuits are passed through with the resistors wired between ground (pin A) and the turn signal supply voltage (pin D) circuits. I mounted each resistor to a aluminum plate for mounting.

Each harness is inserted at C119 or C120 and the resistor plate is attached to a stud that hangs off of the HID module using a M6-1.0 nut.

Sylvania 4157A

Here's a parts list for the wiring harness:

Quanity Delphi Mouser Description
2 15326647 829-15326647 GT 280 5-way connetor (male)
2 15326642 829-15326642 GT 280 5-way connetor (female)
6 15304731 829-15304731 GT 280 terminal (20AWG male)
4 15304732 829-15304732 GT 280 terminal (14AWG male)
6 15304719 829-15304719 GT 280 terminal (20AWG female)
4 15304720 829-15304720 GT 280 terminal (14AWG female)
12 15366065 829-15366065 GT 280 cable seal (orange)
8 15366067 829-15366067 GT 280 cable seal (tan)
2 15430895 829-15430895 GT 280 Secondary TPA (5 way)
4 15317832 829-15317832 GT 280 CPA lock
2   71-RH50-6.0 Power Resistors 50 W 6 Ω 1%

Notes


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Craig Leres