Proper Ground Circuit Diagnostics and Repair
There is not a type of farm equipment that has not been exposed to the integration of electronics. Today we have electronic diesel engines, advanced planters with precision controls and sensors, along with combine cabs with enough monitors that to the untrained eye, one would think it is the space shuttle!
All of this has helped increase crop yields and make farming more profitable – that is when they work. Technology is a beautiful thing, but it is a double-sided sword – a real headache when things go wrong.
When trying to figure out why an electrical device is not functioning, most of us apply the logical step of grabbing the voltmeter and checking the power supply.
The conventional wisdom being if it has power, it should work. If not, the problem must be in the component – a faulted logic that often leads us astray.
Confirming the input voltage is only half of the equation – a D.C. circuit needs a proper ground to function correctly. When confronted with an electrical device that is either not working or showing misbehavior, the proper protocol is to confirm the input voltage with an accurate meter.
If the voltage is correct, your attention needs to be focused on the circuit’s ground side. A circuit can have the voltage supply, or the ground switched on and off.
When working with electronics, the proper mindset is to accept that there is no predictor of how the circuit will respond with a poor ground in most instances.
The test procedure is straightforward. The circuit that is being tested must be powered-up and activated, so you may require a helper. Place the meter’s negative lead on the battery negative cable and the positive lead on the ground being test. Activate the circuit and read the meter.
A good ground will have a maximum of 2/10th (0.20) of a volt on the circuit. Anything more than that, and the ground is poor.
A common mistake that both farmers and professional mechanics alike make is not resurfacing the flywheel when a clutch is replaced.
Though the flywheel is made of heavy-duty material, it is exposed to friction heat even when the clutch disc and pressure plate are not slipping. Over time, this thermal cycling will degrade, warp, and change the surface metallurgy (hard spots).
When this occurs, the clutch has the potential to chatter, vibrate, grab, and stick, along with the premature failure of the new disc and pressure plate. The clutch is designed to work on a parallel surface.
A worn, cupped, or crooked flywheel can also cause release problems, especially in an application that does not have a good deal of inherent travel. If the clutch was slipping before being renewed, an excessive amount of heat was induced to the flywheel. All areas of concern are amplified.
A new clutch assembly that is mated to a flywheel that was not surfaced will have a dramatic reduction in service life. To access most clutch assemblies, the tractor often needs to be split, not a task you want to do twice. If the clutch is worn, then the flywheel needs to be resurfaced; it is that simple.
The proper method would be to take measurements with a dial indicator and magnetic base. At the same time, the flywheel is still attached to the crankshaft. The pragmatic being, if the disc is worn, the flywheel is distorted.
Excessive flywheel run-out is usually the result of previously misaligned resurfacing methods such as on a brake lathe or sloppy fixturing to a flywheel grinder. When I purchase a new flywheel, I bring it to the machine shop, set it up on the grinder, and dress to make sure that it is true.
Do not assume because it is new, that is the case. The market is rife with inferior quality imports and rough handling during shipment.