Saturday, November 26, 2016

LED brake + turn light upgrade for my 2017 Chevy Volt

When a friend of mine bought a used Prius several years ago, he told me that the first upgrade he did was to replace the incandescent brake lights with LEDs.  His reasoning was that LEDs light up a lot faster than filament lamps providing an earlier warning to someone behind that he is braking.

I was surprised to find that my new 2017 Chevy Volt still had old-style incandescent lamps, so I decided an upgrade was in order.  But first some geekery!

I wanted to quantify exactly how much quicker LEDs light up than incandescent lamps so I set up a bench test to compare the two.  

I connected each style of lamp to a 12 V battery with a switch and then used my oscilloscope to look at the switched power (yellow) and the amount of light as measured using a photocell (blue trace).  What I learned was that incandescent taillights take 80-100 ms to reach full brightness whereas LEDs come on almost instantaneously (50 ┬Ás = 0.05mS).  If you are traveling at 60MPH (88ft/sec.), 80mS is equal to about 7 feet.  Clearly this could be a life-saving difference at speed on a freeway.

brake and turn lamps original vs LED
My go-to source for all things LED is because they have excellent selection tools to help you find exactly the lamp you need for your vehicle or any other application.  I quickly found the LEDs I was looking for and decided to also get some turn indicator lamps as well.  So for less than $40 I was able to replace all four lamps in the rear of the vehicle.

The 2017 Chevy Volt manual clearly shows (on p.261) how to access the lamps by removing two Torx screws and one Philips screw.  Then you have to pull the tail lamp assembly forcefully back until it snaps free.  

Each lamp is accessed by twisting counterclockwise to pull the socket out.  The lamps simply pull out of the socket and the new ones push in, although the new lamps required a lot of force to get into the socket.

Here is the new LED in the socket ready to be inserted in the assembly.  Unfortunately, the new lamp was very slightly larger than the old one and would not go in the hole in the housing.  So I used my Dremel tool to open up the hole very slightly and it went in just fine.

After I had installed both lamps on one side It was easy to see the difference and how quickly the lamp switches on and off in the turn signals. unfortunately, the turn signal started to hyper flash.  This is a condition where the vehicle responds to the lower power draw of the LED light and starts to blink very quickly.  The solution is to install a Load Resistor Kit from to trick the vehicle into thinking there is a higher load on the circuit. 

Hopefully I'm never in a situation where I am braking hard on a freeway with someone following closely behind, but I feel that this simple upgrade is a nice performance and safety improvement for the vehicle.

If you are considering a similar upgrade, be advised that all third taillights utilize LEDs, so they illuminate almost immediately compared to the two other brake lights, so you do have the advantage of at least one LED brake light in place in recent model vehicles.  I just like the enhanced response time and visibility.