Testing Seed Tube Sensors
Apr 15, 2012
It's annoying to have one or two rows on your planter's seed monitor show either "failure" or consistently low population. Have those rows truly failed, are they really planting several thousand seeds per acre less than other rows? The only way to tell is to get off the tractor and dig.
If digging proves the rows in question are actually misplanting, then you have to figure out what mechanical aspect of the planter is causing the problem. But if the planter is planting correctly, then the problem is in the seed monitoring system, and it's time to do some diagnostics.
If a row shows complete failure on the seed monitor, my first suspicion is the seed tube sensor. There are a couple ways to check a seed tube sensor. One way is to swap the questionable sensor to another row, and see if the problem follows the questionable sensor to that row. I prefer to use a seed tube sensor tester, purchased from Ag Express, that I can plug into the sensor as it's mounted in the planter--it saves removing seed boxes to access and swap sensors. I just dance a long plastic zip tie up and down past the sensor's "eye" and my tester beeps every time the zip tie moves past the eye--if the sensor is good.
Don't waste time taking a sensor off a seed tube and cleaning or tinkering with it. Seed sensors either work or they don't. You may be able to see the cause of the failure (the lenses often get fine scratches that look like a haze, that prevents the sensor from monitoring accurately) or the problem may be internal and invisible. Either way, it's junk. Strap on a new sensor and see if that cures the problem.
If the the monitor still shows low or no seeds being planted by a specific row, it's time to check wiring. Carefully, patiently check every inch of wire from the seed tube sensor all the way to the backside of the monitor in the tractor cab. Key points to check are where the wires are routed through the parallel linkages right at the planter unit; anywhere the harness passes through a hinge area on a folding planter; and at the back of the tractor where the planter's hitch and the tractor's 3-point can often catch and crush wiring harnesses.
Broken or frayed wires are obvious culprits. Less obvious and more insidious are "flattened" wiring harnesses that are the result of either getting flattened between metal components of the planter, or due to the harness being stretched so much that the wires inside separated even though the outer rubber sheathing stretched and didn't break. Either way, the only way to check is to use a knife and remove the outer sheathing to determine if any wires inside are damaged.
Don't panic and think the actual seed monitor console in the tractor has gone bad until you're certain all the seed tube sensors and wiring harnesses are functioning properly. Seed monitor consoles are remarkably reliable--but they do sometimes fail. Check the cheap stuff first, before you send the console for repairs.
And, if you're desperate to finish a field, but reluctant to plant "blind," consider how many acres your grandpa planted without any sort of seed monitoring system. Talk about an act of faith...