David, you need to find the following wires:
1. Constant power. This wire will have power regardless of the ignition switch.
2. Fog light "activation" wire. It turns "hot" when the foglights are on.
3. Switched power. This wire has power only when the ignition switch is on.
4. Good ground.
You say I need a tester for these? Why can't I just find wires that I know what they are? For example, wires in the fuse box for the fog lamp, an ignition wire... (can't I just hook it to anything that will go on when the car is on? my cd player is hooked to the cig lighter...), a ground (anywhere), and a constant power... (?).
I am going to order the relay as referenced above. Then I will buy some wire. Can I just do this from circuit city (car audio wire)? If I am not mistaken, the whole 'system' of wires and the relay will be run directly around the fuse box, correct?
Won't I need an inline fuse too?
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)