May 19, 2013
I've run into this problem four times in the past two weeks, so I thought I'd mention it:
If the vision of your planter's seed monitor system suddenly is no longer 20/20 (hint, hint) and you have one section or the entire planter's seed tube sensors go off-line, be suspicious of a cut, crimped, pinched or damaged sensor wire to one of the row unit seed sensors.
Twice I found a seed tube sensor wire had been pinched by the parallel arms that support the planter unit. Once I found the sensor wires had been zip-tied to the cross-tube just ahead of the row unit's seed box, and as the unit was raised and lowered the sensor wire sawed back and forth between the zip-tie and the tube and eventually wore through the wire's insulation and shorted out. The fourth "blind" planter was due to one row's seed tube sensor wiring harness connector getting crushed in a down-pressure bracket.
In two of those situations, when the wires shorted the control box that gave the system 20/20 vision was damaged by the electrical mishap and had to be replaced. The other two times the control box survived, and simply splicing the damaged wires fixed the problem.
As always, these are one man's experiences, based upon four separate cases over a two-week period. Take it for what it's worth. If it helps diagnose a problem and gets you back to planting--cool!