1994 Aerostar dies at all times suddenly

1994 ford Aerostar
3.0? V4?
over 100,000 miles
2 wheel drive
this van has had a gradually worsening electrical problem over the past 2 weeks. At first the instrument panel seemed to blink but rescently it will just die as it is being driven.
I believe it is a red wire that attaches to a pin on the upper starter solenoid. If we giggle it the interior lights will come back on and the van will start. We have tightened the battery cables.
I susspected this wire from the beginning but how do I tell where it is broken? Is it feasable to bare the wires and reconnect and wrap using electrical tapeand / or wire nuts?