In The Shop


As a farm machinery mechanic and writer, Dan brings a hands-on approach that only a pro can muster. Along with his In the Shop blog, Dan writes a column by the same names as well as the Farm Journal Shop Series for the magazine. Always providing practical information, he is a master at tackling technical topics and making them easy for all of our readers to understand. He and his wife, Becky, live near Bouton, Iowa.

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.

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