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 name as well as the Shop Series for Farm Journal 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.
In The Shop: 7-Pin Problems
Feb 17, 2011
A warm spell this week prompted a few farmers to start tinkering with planters and other spring equipment, and we got our first calls related to no electrical power to the planter or whatever piece of towed equipment the farmer was working on.
Planters, seeders and most other towed implements get their primary electrical power from the 7-pin connector on the back of the tractor. Sometimes called a "trailer outlet," 7-pin connectors are those round electrical sockets under a hinged cover that have 6 round pins encircling a central pin.
If you're having trouble getting power to a towed implement, before you start tearing apart wiring harnesses on the implement, take a moment to probe the pins on the tractor's 7-pin socket. The top pin--also the longest pin--is the ground. The center pin is usually power, and should carry 12 or more volts. The pins at 1 o'clock, 4 o'clock, 7 o'clock and 10 o'clock in the socket carry turn signal/warning light power, or power to other peripheral systems.
If you don't have a multimeter or test light to check for power, carefully pry back the rubber boot on the backside of the 7-pin power socket and check for corrosion or broken wires. That rubber boot seems to hold water INSIDE the socket better than it keeps water OUTSIDE the socket, so it's very common to find the terminals rotten with corrosion and often completely broken away from their respective wires.
If all the wires and connections are bright and shiny, and the pins show proper voltage, THEN it's time to start probing and checking wiring harnesses on the implement. But I'd guess that 30 percent of the time, the cause of no or low power to implements can be traced to problems with the 7-pin electrical socket on the back of the tractor.