Wire Identification / Brake Light Issue - M1009

[cmroles]

I've been experiencing this problem since I've had my M1009. What happens is that when I hit the brakes, the front-left marker light illuminates (along with the brake lights).

Today while poking around in the engine compartment I noticed one of those wire-tap things clipped between 2 wires on the main firewall terminal block. The tap was clamped between the light-blue wire (Front Marker Light) and a yellow wire that I haven't been able to identify. The yellow wire disappears into a bundle that runs under the truck and disappears. I tried to follow it, but just can't quite figure out where it goes.

I removed the tap to see what would happen, and the brake-light / turn-signal problem went away. Its obvious that the issue was being caused by tapping the marker light into something else.....the question is WHAT is that yellow wire?

I've tried out all the lights (they work) and the truck runs fine. I've been through the diagrams in the -20 Appendix, but am not seeing it.

My concern is that somebody "jimmy rigged" this to get SOMETHING to work, but I just can't figure out what....

 

[Warthog]

The light blue wire feeds the left front park light and side marker.

The yellow wire runs to the rear left stop light.

On most vehicles the following wires colors apply to rear light s and trailers:

brown - park lights
green - right stop and turn
yellow - left stop and turn

 

[cmroles]

The light blue wire feeds the left front park light and side marker.

The yellow wire runs to the rear left stop light.

On most vehicles the following wires colors apply to rear light s and trailers:

brown - park lights
green - right stop and turn
yellow - left stop and turn

This explains why the front left marker would come on whenever the brake pedal was pressed! My concern is why the wires were shorted together with this device in the first place. Is there any reason that you can think of this would have been done?

Thank for all your input on this (and other) threads Warthog!