- The value of the resistors you will need to use is based on how much current your LED bulbs draw. Any values mentioned here are for my LEDs and may not translate directly for you.
- It is definitely possible to make the modification in such a way that the bulb-out detection still functions (i.e. if a bulb is missing or goes out that side will hyper-flash), but my final result doesn't have that. I did have it working at one point, but got too lazy to fine-tune the resistance to make sure it stuck around.
- Remove steering column cover. First, I removed the lower part of the plastic steering column cover. This can be done by removing the two Phillips screws that face the driver's seat. You'll need to rotate the steering wheel to get access to both of them. After the screws are out, you can gently pull the two halves apart, and carefully pull the bottom half out from the dash. The "proper" way to do this probably involves removing a lot more of the dashboard, but I managed without damaging anything. Tip: it may help to unlock the steering column so you can move it around a little bit to work things free. When you're done, you should have a decent view under the dash:
- Unbolt flasher module bracket. The flasher module is a blue (or at least it was blue for me) box that's attached to a bracket right next to the fuse box and has a cable with several wires connected to it. You can't slide it off the bracket where it is because the fuse box is in the way, but you can remove the bracket. There are two bolts that hold the bracket in place. You should be able to get to the first from underneath the dashboard (i.e. by laying down by the pedals). You can see the lower bolt circled in red , and the wire connector off to the right:
You should be able to get to the upper bolt through the hole you've opened up in the steering column. You'll need a small socket driver or wrench as the clearances are pretty tight, but once it's loose you can just use your fingers to get it the rest of the way out. Tip: At this point, if you haven't already, it's probably a good idea to pull out the little door in front of the fuse box so you can see what's going on better. You can see the hole where the upper bolt was circled in red:
- Open up flasher module You should now be able to disconnect the wires from the module and free it from under the dashboard. There are two tabs holding the module to the metal bracket (circled in red) that you'll probably need to use a screwdriver on. There is a black plastic cover on the bottom of the module that is held on by two tabs on the sides (in green) that you'll also need to remove.
You should then be able to just slide the circuit board out of the blue box:
There are two shunt resistors (metal loops) on one corner labeled RS1 and RS2. RS1 is the resistor for the left circuit, and RS2 is for the right. I can't think of any situation where you'd be using different bulbs on one side or the other, but if you run into problems and need to troubleshoot, it'll be good to know. Here's another view of the resistors:
- Replace resistors. So now the tricky part. I wasn't able to find any spec sheets for the IC on this board, so I don't have any exact equations for determining proper resistor values. There are specsheets for the Amtel IC used by non-DTRL flashers though, and I imagine the ciruit is similar. Basically, the stock shunt resistors will be something on the order of 30 milliOhms. The more current per circuit, the lower the resistance. So conversely because LEDs will be using a lot less current, we need to raise the resistance values.
The DTRL LEDs I got draw about 200 mA (as determined using a multimeter and a 12v power supply) and the rear signal LEDs draw about 100 mA, for a total of 300 mA for one side. Like I said, I don't actually have an equation to determine the exact resistance required, but you'll probably be looking for something in the 100-500 milliOhm range.
It might be easiest to start with a 470 milliOhm resistor (which was just barely too much for my 300 mA circuit), and solder on different valued resistors in parallel until you get the result you want. I used 1watt resistors to be overly safe, but 1/2watt should be fine too. Here's what the initial replacement looks like:
And here's the final product after I brought the resistance down a little bit with some parallel resistors:
When all was said and done, I'd used a .470 Ohm resistor first (which was a tiny bit too much; see below for how I could tell it was too much), and a 4.7 Ohm resistor in parallel to bring the total resistance to .427 Ohms. This is enough to prevent hyper-flashing, but still a little too much to allow the bulb-out detection to work (i.e. if I remove one of the bulbs, it still flashes at normal speed)
- Test the modifications. To test, I slid the circuit back into the blue box (so nothing shorted on the metal dash parts), but left the cover and bracket off and just plugged the module back into the cable. Make sure you test with the headlights on, headlights off, DTRLs on and off, and the emergency flashers! The module expects different amounts of current for these different situations and your blinkers might work fine in some conditions but not others.
- Re-assembly. Putting things back together should be pretty much a reverse of disassembling them. Personally, I would suggest that before you go through the trouble of re-attaching the bracket, that you plug in the module and drive for a couple days to make sure everything works correctly. Different situations affect the circuits differently, and you may need to still make modifications (after my first attempt, the right-side blinker would hyper-blink only when the headlights were on and I pressed the brake pedal, lol).
- If your blinkers flash only once and then stop, you have too much resistance for the bulbs you have installed. This will happen if the resistor is not connected (no resistor basically equals infinite resistance), the resistor value is too high (try a lower valued resistor or connecting a resistor in parallel), or the bulbs you have are drawing too much current (e.g. if you left the incandescent bulbs in-place of the LEDs).
- If your blinkers flash twice as fast as they should, you have too little resistance for the bulbs installed. This will happen if your resistor value is too low (try a higher valued resistor), or your bulbs are not drawing enough current (e.g. you put LED bulbs in without modifying the flash module)
- Test under all conditions! Headlights on or off, DTRLs on or off, hazards on or off, etc. If you're right on the borderline, even small fluctuations (like the brake lights turning on or off) might make the flashers stop working or hyper-blink. Also the longer bulbs and circuits run, the warmer they get, and their resistance increases slightly.
- You can connect resistors in parallel in different combinations to make adjustments without having to re-solder through the holes in the circuit board. The total resistance will always be less than the lowest-valued resistor, and you can find calculators online to help you with figuring out the values to use.
- If you want bulb-out detection to work correctly, you'll need to tune the resistance so that with one bulb out you get hyper-flashing, but with all the bulbs in things flash normally. The module appears to compensate for the headlights being on, so it may only be possible to get the detection to work while the headlights are on. As I said, I didn't have the patience to figure it out, but in theory with the correct resistance it's doable.