SMART JUNCTION BOX (SJB) Programming??? Schematic???

[JamaicaJoe]

2013 XLT Expy.
I have very terrible lighting on my instrument cluster. I have the shop manual for the wiring and apparently there is some logic in the SJB that provides "rules" for the cluster lighting. For example the variable control on the dashboard does nothing. The headlights must be on for any backlighting of the gauges, fuel, battery , oil, temp etc. so that the needles show up. During daytime they are off. The design of the panel blocks outside light with shadows. The sun sensor works but does not aid in the decision. According to the operator manual it is "normal". I would like to reprogram the SJB to turn the back lights on and perhaps allow variable intensity from the roller knob.

What software is required? Does anyone have an actual schematic of the internals of the SJB? Failing a reprogram, I might be talented enough (over 45 years electronics engineering) to add a diode or two to make this happen without reprogramming.

 

[Anonymous98]

Alldata DIY - Get a subscription specific to your vehicle, and you will have the wiring logic, the cluster illumination logic, the circuits to check and in which order, and color-coded diagrams of every circuit, the fuse circuits and values, connectors, grounds, ABS MODULE, SJB, Battery Junction Box, and of every other electronic component in your vehicle at your fingertips. I did this and it helped me solve a lot of problems in my 2010 Eddie Bauer 2WD Expedition.

 

[Expensedition]

Hi JamicaJoe,

A lot of the field devices look like analog devices. maybe inserting a resistor at the light sensing device, perhaps start with a decade resistor and find the value that gives you the result you are looking for? You could measure what it is at a known amount of light and either go up or down and see what happens.

You know the process: FA and FO

Always loved the Joy of success.

As A98 says: "Get a subscription specific to your vehicle"
Tech pubs are the way to go if you can get one. Ebay is a good source for that.

V/r

SM

 

[JamaicaJoe]

I will check out ALLDATA to see if it is more informative. The 400 plus pages of the FORD electrical manual are not very helpful as it is less a schematic (than the old Haynes wiring diagrams) and more a block diagram of interconnects, lacking any continuity details. As I mentioned the Sun Sensor does not do much. The backlighting is wired to headlight position. In my Gen 1 Expy I can roll the intensity dial to a mode where the instrument lighting is on regardless of headlights. Compounding this is the white and chrome layout and clutter of the instrument cluster that detracts from visualizing the gauges.

 

[Anonymous98]

Same problem with my 2010 Eddie Bauer Expedition (2WD). Would love to find the answer.