Preseason through post-season, combine and moisture monitor maintenance will help keep your machine fit and accurate for harvest.

A long productive life for a combine is not an accident. Harsh conditions in the field will eventually wear away many critical components. Growers expect to do routine maintenance on cutter bars and chains, but as a combine begins to reach old age, bearings fail, rasp bars and concaves become worn, and massive steel parts on the feederhouse, rotor and other components can erode away to nearly nothing.

A little preseason preventive medicine and even some minor surgery can keep things running smoothly and help prevent costly parts failure in the middle of good harvesting weather.

Repack
Repack sealed bearings with grease and inspect rotors or cylinders and concaves for proper clearances when set according to manufacturer specifications. There is no general rule of thumb for when to replace worn parts, but when significant compensation needs to be included with factory settings to achieve proper clearances, that's a sure sign that threshing action is already compromised and that further wear is more likely to cause sudden failure in crucial components.

Cleaning
A combine is a naturally dusty and dirty machine. So just how important is combine cleanliness to combine performance? As soon as the combine rolls down through the field all the cleaning in the world may seem like a wasted effort.

The many layers of residue that collect on combine parts usually consist of more than just dust. Long hours in the field typically lead to the most amazingly well-constructed nests of dust, stems and grain that can hide the underlying machinery and potentially obstruct proper operation of combine components. Every new accessory seems to become just one more place for the dust to settle and a potential home for insects and rodents.

Periodic cleaning throughout the harvest season can head off potential problems before they have a chance to cause any real damage. Piles of dust and dirt can trap moisture and corrode metal parts. Keep shields in place while the machine is in use, but at the end of the day or whenever the opportunity arises, open access doors and remove shields for a thorough cleaning. In particular, routinely inspect and clean the engine compartment as needed to reduce the risk of fire.

Repair any fuel or oil leaks--defects that add fuel to any potential fire.

Before performing any maintenance always shut down the engine and remove the key. Then remove all panels and access doors to thoroughly clean any area where grain can become trapped.

While cleaning, pay particular attention to areas that support electrical wiring. Aftermarket wiring harnesses for yield monitors and related accessories should be installed securely and in such a way that they are not susceptible to becoming snagged by debris. The cleaning process itself can sometimes become the cause of damage to electrical wiring as large pieces of debris are removed. Compressed air is often the best way to unravel the intricately--woven nests of dust and debris, especially in areas where it has formed around electrical wiring.

Clean and accurate
Daily inspection of the mass flow and moisture sensors for yield monitoring systems also helps ensure good performance and reliable data. Keep an eye on yield monitor measurements and take a moment to inspect sensors anytime you suspect the data doesn't seem to reflect actual field conditions. In particular, check and clean moisture sensors often, especially after operating the combine in weedy or damp crops. Sudden changes in moisture readings may be a sign that the moisture sensor is covered with plant sap or debris. A sudden change in yield could be an indication that debris has collected on the sensor. Many sensors now incorporate active cleaning components to scrape away debris or a buildup of plant sap that may have collected on the sensor surfaces. Spot check moisture and yield measurements with other means to determine if on-board systems are working correctly.

Storage tips
Combines simply backed into the shed without good cleanup provide a haven for rodents and birds. Poor equipment hygiene can lead to problems in long-term storage. As the 2003 harvest wraps up, take time to thoroughly clean and lubricate combines and accessories to preserve and protect them until harvest begins again next year.

This is also a good time to assess wear and the condition of the moisture, temperature and mass flow sensors. A worn mass flow sensor, in particular, can begin to cause erratic readings as the shape of the sensor surface begins to change from the abrasive action of hundreds of thousands of bushels of grain.

It is sometimes possible to remove more than a bushel of grain even after a combine seems to be clean. Trapped grain attracts rodents, which often make a meal of electrical wiring as well, leading to short circuits or other electrical problems. Mouse-chewed upholstery in the cab may be little more than an annoyance, but can damage seats so badly that they need to be replaced. Birds that use a stored combine for its relative safety and as a source of food leave nests that can become a fire hazard. In many cases the damage to combines from rodents and birds is easily fixed, but it makes more sense to prevent the damage in first place.

Thoroughly remove debris, which can trap moisture and cause rust or corrosion. Compressed air is a great way to clean hard to reach places and may be a better choice than water especially on electrical components where eventual corrosion can create a voltage drop that ultimately results in poor performance.

William Casady is an agricultural engineer for Commercial Agriculture at the University of Missouri.