I replaced the front turn signal bulbs with LED bulbs and saw the dreaded hyper blink. I had my load resistors ready (to draw the same amount of current as the stock bulbs), but it seemed like a horribly brute force way of doing things. A little searching on the web brought me to people that disabled the hyper blink feature of the stock relay ( http://www.yotatech.com/f2/cheap-bastards-idiot-guide-fixing-fast-blinkers-after-led-swap-80626/ ). I took that one step further by keeping the bulb failure sense in place by modifying the relay circuit. You need to be able to solder for this mod.
Why?:
The stock turn signal relay has an integrated circuit inside with the relay. The IC looks at the turn signal current flow. When you left turn signal is on, the current of both the front and back left turn signal flow through the relay. If the current is a lot less than it should be, then it assumes a bulb burned out and flashes the good bulb very fast. When you use LED bulbs, the current is low and the circuit thinks there is a problem.
1 Take apart the dash just below the steering wheel. Steps 6 - 8 of this tech article show how to do it http://www.customtacos.com/tech/index.php?article=77
2 You now can see the fuse box under the dash near the driver's side door. The turn signal relay is on the back side of the beige fuse box.
It is up near the top of the fuse box (back side). Here is the view you get with your head down by the brake pedal. You can remove the fuse box or just reach up there and grab it. I left the box in place. The arrow points to the relay.
3 Pop the cover off the relay by pushing in on the tabs. There is that IC that causes the hyper flash.
The turn signal current flows through a resistor causing a very small voltage drop that the IC can read. The resistor is about 30 milliohms. The red tool is resting on the resistor (basically a a wide piece of metal).
4 You need to change the value of the resistor so it doesn't go into the hyper blink mode. The resistance needs to go higher. There are two ways to do this. You can buy a resistor from places like Mouser, Digikey, or possibly Frys or you can modify the stock resistor. I took the Dremel and started making the stock resistor more narrow. That increases its resistance. I had it right about where it needed to be when the Dremel tool threw it. I never did find it. I wound up using some resistors I had laying around (three in series to get what I needed). Shaving the stock resistor down is probably the easiest, but measuring the value as you go is a problem since most volt/ohm meters can't measure that low with any accuracy. Here are my three surface mount resistor I used soldered in series and in place. A single through hole resistor would be ideal.
Choosing your resistor value:
You could just shave/trim the stock resistor and keep checking to see if your hyper blink goes away. You should unsolder the stock resistor to either shave it or replace it.
The stock relay is setup for incandescent bulbs. The front and back set (left set or right set) draw about 4A total (2A per bulb). If one bulb dies then you only have 2A. They put the hyper flash trip point near 3A (high enough you won't get false triggers, but low enough to catch a bad bulb). When less than that current flows the voltage drop across the resistor falls below the fixed 80mV trip point for the IC (80mV is set inside the IC).
For example, lets say you are using front and rear LED bulbs for turn signals. These bulbs draw about 1/2A each for 1A total. You want the trip point to be above 1 bulb, but below 2 bulbs so pick 0.75A. Now a little ohms law. (0.75A X resistor value) = 80mV. 0.75A / 0.08 = 0.11 ohms. Call it 100 milliohms. Replace the resistor with 100 milliohms and you should be set. Use a resistor rated at 1/4 Watt or higher. Higher rated power resistors are best as long as they fit inside the relay case.
Matt
Why?:
The stock turn signal relay has an integrated circuit inside with the relay. The IC looks at the turn signal current flow. When you left turn signal is on, the current of both the front and back left turn signal flow through the relay. If the current is a lot less than it should be, then it assumes a bulb burned out and flashes the good bulb very fast. When you use LED bulbs, the current is low and the circuit thinks there is a problem.
1 Take apart the dash just below the steering wheel. Steps 6 - 8 of this tech article show how to do it http://www.customtacos.com/tech/index.php?article=77
2 You now can see the fuse box under the dash near the driver's side door. The turn signal relay is on the back side of the beige fuse box.
It is up near the top of the fuse box (back side). Here is the view you get with your head down by the brake pedal. You can remove the fuse box or just reach up there and grab it. I left the box in place. The arrow points to the relay.
3 Pop the cover off the relay by pushing in on the tabs. There is that IC that causes the hyper flash.
The turn signal current flows through a resistor causing a very small voltage drop that the IC can read. The resistor is about 30 milliohms. The red tool is resting on the resistor (basically a a wide piece of metal).
4 You need to change the value of the resistor so it doesn't go into the hyper blink mode. The resistance needs to go higher. There are two ways to do this. You can buy a resistor from places like Mouser, Digikey, or possibly Frys or you can modify the stock resistor. I took the Dremel and started making the stock resistor more narrow. That increases its resistance. I had it right about where it needed to be when the Dremel tool threw it. I never did find it. I wound up using some resistors I had laying around (three in series to get what I needed). Shaving the stock resistor down is probably the easiest, but measuring the value as you go is a problem since most volt/ohm meters can't measure that low with any accuracy. Here are my three surface mount resistor I used soldered in series and in place. A single through hole resistor would be ideal.
Choosing your resistor value:
You could just shave/trim the stock resistor and keep checking to see if your hyper blink goes away. You should unsolder the stock resistor to either shave it or replace it.
The stock relay is setup for incandescent bulbs. The front and back set (left set or right set) draw about 4A total (2A per bulb). If one bulb dies then you only have 2A. They put the hyper flash trip point near 3A (high enough you won't get false triggers, but low enough to catch a bad bulb). When less than that current flows the voltage drop across the resistor falls below the fixed 80mV trip point for the IC (80mV is set inside the IC).
For example, lets say you are using front and rear LED bulbs for turn signals. These bulbs draw about 1/2A each for 1A total. You want the trip point to be above 1 bulb, but below 2 bulbs so pick 0.75A. Now a little ohms law. (0.75A X resistor value) = 80mV. 0.75A / 0.08 = 0.11 ohms. Call it 100 milliohms. Replace the resistor with 100 milliohms and you should be set. Use a resistor rated at 1/4 Watt or higher. Higher rated power resistors are best as long as they fit inside the relay case.
Matt