Help identifying illumination wire on cargo light switch

You're reading the power from the fuse (hot) passing through pins 86 (coil) then to 85. If you had someone outside watching the lamp, you'd see that you are energizing the relay thus turning on the lamp with your meter reading...

 

Thank you, that was my assumption but not the behavior I'm seeing.

When the cargo light is on (door or On switch) I get zero volts on Pin5 (blue switch).
When the cargo light is off (door closed or Off) I get 12 V + on the switch pin 5 and the Cargo Light is Off.

The diagram shows the Cargo Relay (pins 1 &3) shorts the battery to the coil...is this somehow a "negative switch" circuit and why is it not shorting out Pin 5 to the battery thought the coil?
Thanks for any insight...I am generally very good at this, but I'm stumped.

 

Just curious...i ran some LEDs to my bed under the cover and the wire setup is just red and black. Can i relay ot to the cargo light main switch.

 

Did you ever figure this out? I just ran into the same situation and came back inside to search the web for answers. It doesn’t make any sense to have 12v from blue to ground in the off position and zero v when the switch is on or in door mode.

 

Placement of the meter probes makes the difference...but be careful not to short the Main Body ECU.

 

I ended up tapping the output to drive a relay:

Pics and descriptions mid way down in this post of my builds:
https://www.tacomaworld.com/threads/cudgels-build-thread.600420/#post-20174389