The red and yellow wires coming from steering box solenoid valve to the wheel arch area had completely disintegrated from years of heat.
The wires were touching inside the thicker black sheath.
I removed removed the solenoid, then cut down the sheaths to reveal fresh wire. I soldered new wires to the two wire ends poking out of the solenoid valve and the other end of the cable where it connects in the wheel arch.
I tested the solenoid, after completing the wire fix, for an Ohm reading.
It was an 8.2 ohm reading.
I've seen working solenoids from this model with 7.5 ohm so I assume mine is in good working order.