Truck is an '01 V 10/automatic.

Hubs stay engaged all the time. I've checked the hubs and lines to them with a vacuum pump (including the line to the HVAC controls), all hold vacuum indefinitely.

When I "tee" a vacuum gauge into the line going from the hub lock vacuum pulse solenoid to the hubs, I show full engine vacuum (about 16" hg) going to the hubs at all times, regardless of the dash selector switch position. (Engine running)

I also am getting 12 Volts on the center pin of the connector to the hub lock vacuum pulse relay. The schematic I've found (https://www.ford-trucks.com/forums/9...esof-help.html) shows this should be 5 Volts (VREF). Other systems powered by the VREF seem to be working fine....

I've searched many threads here, and have not seen any reference to these test results

The transfer switch shifts normally from each mode to next. All fuses are good and the ESOF relays check out fine. I replaced the vacuum hub lock solenoid in August with a new Motorcraft unit from Ford.

So, my questions: where is the 12 V coming from? Where is the 5 V (VREF) sourced? Would this voltage damage the hub lock vacuum pulse solenoid? Why the constant vacuum? In other words, I've about worn out my "bang head here sign," how do I fix this one (!) ???
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