We must demand schematics for our electrical systems

Monday, December 6, 2010

Let us collectively tell the major equipment manufacturers that we need direct access to the layout of the working systems for the equipment on which we spend big dollars

by RALPH WINFIELD

Electrical faults that "come and go" can cause serious frustrations and take machines out of service at critical times, such as harvest days when time is big money.

About a year ago, I introduced this issue and suggested that operator's manuals should contain electrical schematics. Those are line drawings that allow any person with a reasonable working knowledge of electrical circuitry to trace current paths by being able to predict voltage indicator points.

Additional personal experiences and comments by neighbours and former students, as well as readers, have increased my resolve to reiterate my case for asking – or should we say demanding – that manufacturers be required to provide that information to equipment purchasers.

Some years ago, I had a problem with the "work lights" on my combine. This meant that, when darkness came, you had to quit combining because the cutter bar, grain bin and unloading auger lights would not work. The driving lights still worked, so you could go home. But, guess what, the next morning the "work lights" would be working just fine! At that time, there was little point in calling for a service technician.

After multiple attempts to solve the problem by putting in a new light switch and, later, putting in the multiple pin holder on the back of the switch, I finally found the real culprit. It was a one-pin fault in a major multi-pin connector in the wiring harness. The ultimate solution was very simple. Jumper that pin connector outside of the wiring harness without compromising the circuit protection. Those lights have been working well for many years now.

More recently, I purchased a new utility tractor. On rare and unexpected occasions, it would fail to start. The starter would crank the engine, but obviously the injection pump was not providing fuel. This is a newer-style tractor with an electrical solenoid in the pump that controls fuel flow. Generally, after two or three tries, the engine would fire up and not create concerns for another 50 starts. Not much point in calling a technician to fix what isn't broken.

Finally, this past summer, it actually burned off the 20-amp fuse for the diesel pump solenoid valve. At last, a definite clue. I tried a 30-amp fuse and burned off the 30-amp start circuit fuse.

The time had come to call for outside help. Armed with an electrical schematic on a CD for his portable laptop, the technician determined that the most likely culprit was a temperature sensor connected in parallel with the pump solenoid. Apparently, this coolant temperature sensor varies the advance of the diesel pump to control emissions on cold start-up.

The sensor was not changed and the tractor started up many times until the sensor shorted out again. It is now permanently disconnected and the tractor starts and runs just fine. My cost for the tentative diagnosis? Just under $300!

The more I talk with other tractor, combine and heavy truck owners, the more I realize that my concerns are not unique.

One answer is to have schematics for our electrical systems. Most farms with a number of larger, sophisticated pieces of field-going equipment have a shop and at least one person on the operator/service team who is able to read schematics and who also knows how to operate a multi-meter that provides voltage, resistance and continuity readings or responses by buzzer.

As electrical systems become more sophisticated, we need schematics that permit tracing of current paths that allow pinpointing of faulty components or connections.

Some equipment suppliers just say, "Bring it to us for service." And, yes, I do not doubt that many dealerships have competent service technicians, but when faults are transient, replacing numerous components can be very expensive.

Most equipment dealers who sell electrical components have a policy of not accepting returned electrical components. I have no trouble with that policy. New electrical components can and will be damaged if they are used as troubleshooting devices.

In Ontario, we have a farm equipment board under the auspices of the Ontario Ministry of Agriculture, Food and Rural Affairs. They look after safety issues with farm machinery and arbitrating disputes, but the website gives no indication that the board has ever taken up the question of a buyer's right to know. Maybe we should be collectively requesting that the board take up this issue. BF

Agricultural engineer Ralph Winfield farms at Belmont in Elgin County.