Originally Posted by Big-E
The red wire with the green strip is in fact the ground wire from the high-beam switching relay located behind the glove-box.
When the car is running, with the headlamps off, there is power being fed to them. Subaru uses a switched ground system to control the headlamps.
Although off, there is power running through this circuit (red wire with green stripe) and it feeds the fog-lamp relay and switch. The relay so you can of course turn the lamps on and the switch so that when its turned on, the little green indicator lamp illuminates.
If for any reason you simply tap into the red wire with the green stripe and not fully disengage it from the relay (whether unlock or cut) you will effectively feed power backwards into the headlamp system, which will cause problems such as blowing fuses.
Good to know! Thanks for the info. Would you happen to know how to fix the problem? Maybe change the wire we tap into?