Bosch sihwasher sms4452gb

My older dishwasher, unknown vintage, is beginning to play up after years of faultless service. Two months ago the float micro switch became stuck, silicone oil resolved that. Now, on beginning the wash cycle; it begins with the initial drain, then, when switching to activate the inlet solenoid, there is an erratic voltage delivery to that solenoid. It does not open the solenoid, so no water will fill. Does this indicate a broken wire in the door hinge area, or is there a failing circuit board in there somewhere?
The siphon and reservoir system is a work of art, would not go amiss as an exhibit in itself!