Combine Troubleshooting Guide

Threshing – Underthreshing
Grain Tank                       Mainly large kernels 
                                       Very little grain damage
Return                             Unthreshed heads
Walkers                          Unthreshed heads, long undamaged straw
Shoe                               Light chaff load

1) Increase cylinder/rotor Speed (limit: grain cracks and shoe chaff                  loading).
2) Decrease concave clearance (limit: shoe chaff load).
3) Put in concave filler blanks (limit: grain damage and separating loss).
4) Decrease feed rate.

Threshing – Overthreshing
Grain Tank                     Cracked, split, peeled kernels              
                                       Short lengths of straw
Return                             Damaged grain
Walkers                          No unthreshed grain 
                                       Straw torn, broken, shortened
Shoe                               Heavy chaff load
                                       Chaff contains a lot of straw

1) Increase feed rate (limit separating loss)
2) Decrease cylinder/rotor speed to reduce grain damage.(Be sure to
     check the return for clean grain first.)
3) Open concave if excessive straw breakup is the  major overthreshing
     problem.

Separating – Poor 
Walkers                          Free grain; more than 2% or Rotors is excessive

1) Take out concave filler blanks
2) Increase cylinder/rotor speed (limit: grain damage)
3) Decrease concave clearance (limit: shoe chaff load,power)
4) Decrease feed rate

Cleaning: Loss – Sloughing
Chaffer                            Grain, chaff dropping just over end of chaffer

1) Increase air blast
2) Decrease chaffer opening
3) Check air distribution, redirect air, usually towards rear of chaffer sieves
4) Open cleaning sieves
5) Decrease threshing and separating aggressiveness
6) Reduce feed rate

Cleaning: Loss – Blowing

Chaffer                            Grain dropping over end of chaffer with chaff                                               beyond Light seeds in air system

1) Open chaffer
2) Direct air blast toward front of sieves
3) Decrease air blast
4) Open cleaning sieve (air may be going under sieve and up at back end)

Cleaning – Light Trash in Grain
Grain Tank                       Light Chaff

1) Look for wind blowing chaff forward into fan inlet
2) Increase air blast
3) Decrease chaffer opening
4) Direct air to dead spots on chaffer or cleaning sieve
5) Close cleaning sieve

Cleaning – Heavy Trash in Grain
Grain Tank                       White caps, part heads

1) Check threshing
2) Close cleaning sieve
3) Increase air blast
4) Use round hole sieve

Cleaning – Grain in Return
Grain Tank                     Excessive grain damage for a reasonable
                                       cylinder/rotor speed
Return                             Carrying a large volume of  clean grain
Shoe                               A noticeable amount of damaged grain particles.                                         Overloading to point of grain loss from section                                              where return is delivered

1) Check route of grain into return. Close chaffer-tailing section. If grain 
     loss increases and grain in return  decreases, it shows late separation on
     chaffer – treat as grain loss.  If grain in the return is unchanged it is going
     over the cleaning sieve – follow next steps
2) Check air distribution, direct air blast to front of sieves or away from
     cleaning sieves
3) Open cleaning sieve
4) Decrease air blast

Cleaning – Light Trash in Return
Return                               Loaded with light chaff, straw

1) Check for wind blowing chaff into fan inlet
2) Increase air blast
3) Decrease chaffer opening, chaffer tailing section opening.  If chaff
     persists:
4) Check route chaff is entering return. It may enter either through tailings
     section or over cleaning sieve. For chaff through the tailing section: Shift
     air towards rear; increase blast or decrease opening.

For chaff over sieves: Check air distribution, front to back and side-to-side and adjust if possible.  NOTE: Windboard at angle to fan throat can cause down drafts: for least disturbance, position parallel to fan throat. Check chaff and grain distribution.  If uneven, try to shift load evenly or to areas of stronger air blast.

Cleaning – Green Material in Return
Grain Tank                       Green Material
Return                             Green Material
Shoe                               Green Material

1) Close chaffer and chaffer tailing section
2) Increase air blast
3) Reduce feed rate

Source: University of Minnesota Extension Service