BACKGROUND: Due to model year wiring differences, I found previous articles describing how to hotwire the fusebox for "fog lights without headlights on" probably wouldn't work on my '89 325i with ellipsoids. After digging thru schematics and probing with a multi-meter, I found a workable solution.
This mod will not work on many E30's, so proceed only if you have sufficient car electronics experience to determine if this is viable on your particular vehicle.
Final warning is this mod will allow the fogs to be left on with the parking lights on and no keys in the ignition. Due to the potential for unintentional battery drain, only proceed if you want the convenience of front lighting with no keys. Do not perform this mod if you might leave the parking lights on without noticing the green fog light indicator and entire dashboard lit up. At the bottom I discuss a second, untested method to have independent fogs with parking lights on and the key in the ignition.
Previous procedures I've read about leave the fogs on even when the high beams are activated. I prefer to follow the BMW design principle of unloading unnecessary power when the high beams are needed, so this mod will disable the fogs when the highs are on.
Required Parts:
- Small length of 16AWG wire
Required Tools:
- Multi-meter
- Wire cutter
- Wire stripper
- Soldering equipment
- Flat-head screwdriver
1. Verify your fusebox has the exact same K3, K4, and K8 relays. This would be the first indication if this method is even feasible on your vehicle. If you have the same colored relays with the same schematics molded on the relay covers, it's a bit safer to proceed.
Use the screwdriver to carefully pry out the K4 low beam and K8 fog light relays. Disconnect your battery prior to doing so if you want to be safe. Reconnect the battery before the next step.
REMINDER: The steps below are crucial to determining if your car's circuitry is similar to the car described here. If anything including relay appearance or circuit test results does not match 100%, do not continue unless armed with detailed schematics of your car's wiring diagram and enough knowledge of car electronics to avoid damage to the circuitry. Severe damage to your vehicle and persons performing the work can result.
2. Use a multi-meter tool to confirm fusebox K4 terminal 87 connects to K8 terminal 30. The terminal numbers are stamped on the bottom of the relays for reference. Probe for 12V hot at all times on K4 terminal 30. To pre-test this mod and only after all the above check out as correct, use a length of wire to bridge terminals 87 and 30 of fusebox position K4. Relay K4 should be removed and relay K8 installed during this test. The fog switch should work when the parking lights are on.
3. Solder a short length of wire between K4 terminals 87 and 30 close to the body of the relay as shown below.
4. Reinstall the relays, with K4 not seating completely due to the soldered wire. Use care when installing K4 because I ran into a issue by pushing forcefully down on the relay, where the low beams came on and stayed on even w/ the keys removed from the ignition. I'm guessing the extra wiring I soldered was pushing up on the base of the relay, causing the internal contacts to touch and engage the low beams. I simply backed off on the install pressure and everything has been fine. Turn on the parking lights + fog switch and enjoy the results.
Alternate Method:
If you wish to modify the procedure to only allow independent fogs when the ignition is on (for safety reasons), find a sufficient gauge+fused switched 12V line and attach it to K8 terminal 30 and do not modify K4 at all. I have not tested this and warn of easily bridging switched power from K8 terminal 86 without researching the gauge and fuse rating that connection uses. E-mail me if you are going to attempt this and possibly I can assist.
