[W126 Coupe] Independent Fog Lamp Operation

[Dick Spellman]

Just thought I'd mention that I finally rewired the electrical circuits 
for the lighting on the 83 SEC.  So, I now have the console rear cabin 
courtesy lamp switch used as a 12volt trigger to a 10 amp 12vdc rated 
relay that powers the fog lamps exclusively and instrument cluster 
mounted 12v indicator led.  The fog lamps will now light without the use 
of the headlamp switch and without the need for side markers.

Additionally, I went ahead and routed the NSE circuit directly to the 
rear fog lamp where I no longer use the NSE for the front fogs.  This 
means that a single pull on the headlamp rotary switch when the switch 
is in some on state will light the rear fog lamp.  I had to add a single 
cable (16ga.) to the rear and add the socket and lamp to the holder in 
the driver's rear tail lamp assembly.

To summarize the set-up for just the independent front fog 
operation...For components I used an Elk 912B relay, Elk wiring 
connectors, 16 gauge stranded wiring (for lamp power and ground); 18 ga. 
stranded wiring (for trigger wiring); and a 12volt LED with the built-in 
resistor.  I used the former cigarette lighter positive feed to provide 
power to the fog lamp common on the relay.  This circuit is only on when 
ignition switch is in ACC or engine running so there is no need to worry 
I've left the fogs on when exiting the car.  I used the courtesy lamp 
power to provide the 12vdc trigger input to the relay.  The rear cabin 
courtesy lamp is now rendered inoperative.  I connected the 2 fog lamp 
positive sides of their individual circuits (removed from the rotary 
headlamp switch)  to the N.O side of the relay.  I pulled ground for the 
LED and the relay trigger from the ground post behind the instrument 
cluster.  I placed the LED in the IC at position 3 and masked off 1/2 to 
reduce the brightness on the IC face just a bit. 

This information is specific to early model 126 chassis with the early 
model screw terminal headlamp switch only.  The Elk 912B relay has  
heavy duty clamping screw terminals and plenty of capacity to handle the 
current on this circuit.  I placed the relay in an accessory box 
directly under the rotary light switch on the lower dash shelf where the 
knee bolster bolts up.  I left cable for the wrapped LED harness so that 
the IC can be removed and items unplugged without tugging on the 
harness.  In other words, neat, clean and properly laid to avoid an 
electrical short or fire.

Regards,

Dick