Hi RedRunner,
Some of the information that you need is on page
(2 of 2) on the diagram below; but keep reading...
The problem that you would have tapping directly into the
'Secondary' (high current load/headlight) wiring is that this circuit is
'HOT AT ALL TIMES' and so, offers no platform for switching control. The Headlights are controlled on the
Negative side of the circuit so when you turn them on, you're not supplying power to the lights, you're providing a ground to complete the circuit. This is known as:
Negative-side switching circuitry; which most late model auto manufacturers have employed today. All of our lights/accessories are hot at all times... that's good to remember when working on the truck's electrical system because just turning an accessory off with the switch
Does Not de-energize that device!
The Wire Of Interest: (Below) This will need to be on the
'Primary' or the control side of this circuit. It's a
PINK wire and runs from the 'Main body ECU' (pg 1 left, see label), and then enters the diagram on pg 2 (below), wire
number 2 at the left-side of the diagram; "See the
BLUE arrows".
After having studied the two diagrams and trying to decided upon the best way to approach the issue of accessing the wire(s) needed to trigger your new 'Inclinometer' light, I don't think you'll be able to locate that pink wire in the Main relay/fusebox because there are
many pink wires running through that main harness to the vehicle's interior. But... there may be a solution to this problem. You could
(1)... Pull the
Headlight relay (
RED arrows, top of diag) from it's base, pick up another (short) relay harness with the same 'foot-print' and tap into the ground lug (Pin #2 on the relay) on that harness. Or
(2)... you can go after the
Dimmer switch harness and find the
Lt Green wire that provides ground to the truck's low beam relay; "See below":
I've placed a green circle around the low beam dimmer switch contacts, and
'Pointed' at that Lt Green low beam ground wire to make it easier to find. It runs through the steering column's wire trough but I've never tried to access it so I can't tell you exactly how to approach it; I'm sure someone else here has done it. Let us know how you make out with this project, it'll be a great teaching tool for this forum,
Rgds
...and cheers! (rigtec)
