Now that I have my HID projector headlights in place (per thread here
), I don't want to have them on at full brightness all the time because of the DRLs (per the discussion here
). Crappa has a solution that he came up with
, but it involved extra external wiring and relays and I thought there MUST be an easier way, so I studied the schematics and came up with the following. It involves modifying two relays and keeps all the wiring inside the underhood fusebox. Plus, it's easily and quickly reversible by just replacing the modified relays.
: The method below causes the fog lights to be used as DRLs. It also (!) retains the ability to switch on the fogs, even if the DRLs aren't on.
First the caveat. I take NO RESPONSIBILITY
for any damage resulting to your car when following these instructions and/or doing this modification. On your own head be it!
So what we're going to do here is simply break the output of the DRL relay and just cross-link it to the coil pin of the fog light relay, as shown in this modified schematic. Thus, no changes need to be made to the car's wiring harnesses:
OK, so a couple of ways to do this. In my case, I bought a pair of Omron relays from Digikey <this>
for just $4 each plus $3 postage - or probably available at similar cost from your local parts store. I then took them apart and internally wired (later). However, a perfectly good option is to cut off the pin from your existing DRL relay and solder the cross-link wire to the correct pin of your fog light relay. This photo shows the two relays (inverted, obviously, since they are upside-down) with the green line showing how to solder the wire and which relay pin to cut off:
Here's how I rewired the Omron relays, should you buy them and want to do it this way. First unclip and pull off the relay shell/cases, then drill a small hole in the top corner of the shells to allow the wire to exit (see the picture to see which corners to drill!).
Then, for the DRL relay, cut the innards and solder the wire as shown (NOTE: this works for this Omron relay ONLY, other manufacturer's relays may be different internally, and certainly the ones in my car from the factory were NOT modifiable internally as the contacts/wiring are enclosed/hidden inside - in which case, you would need to use the external method above) [whew!]:
Now feed the wire through the two relay cases (don't forget to do this before soldering!!), then solder the fog light relay like this:
Finally, now you have your relays wired together, simply go to your car and open the fusebox (below). Unplug the foglight relay #54 and the DRL relay #48. Replace them with the modded ones. NOTE THE ORIENTATION
-- any other connection could blow a fuse or even fry your BCM! To confirm, see the red-sharpie arrows on the relays, pointing to the big red Positive terminal on the fusebox.
Close up the fusebox and you're done! Reversing it is a simple matter of replacing the two relays with unmodified ones.
Hope this helps anybody who has HIDs and doesn't want them on all the time