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John Deere Combines 6620, Side Hill 6620, 7720, 8820. Hydraulic Operations and Tests - part 6

The header height control system for the 8820 Combine consists of the following components:

Two header lift cylinders (A) (Fig. 2A) which raise and lower the header. Refer to Section 270 for information on these cylinders.

Secondary control valve (B) (Fig. 2A) and unloading auger cylinder (K). Oil for the header height control circulates through these two components.

Drop rate valve (C) (Fig. 2A) controls the speed of header drop. See this section for information on this vaive.

An auto header valve (J) (Fig. 2A) equipped with two solenoids transfers electrical energy to hydraulic energy to operate the system. See this section for operation and service of the valve.

An oil cooler |G) (Fig. 2A) is used to cool the oil for the header height control circuit. This oil also passes through the reel speed valve (H) and reel drive pump (I)-

Main system reservoir (E) (Fig. 2A). main system control valve (D), and main system hydraulic pump (F) provide the basic hydraulic Mow for the system. See Section 270 for information about these components 

Header Not Activated

The electrical system has not activated either solenoid on the auto header valve (L, Fig. 3). The pilot check valve in the auto header valve and the lockout poppet in the main control valve (E) close, trapping oil in the header lift system.

Pressure free oil now flows from the reservoir (I. Fig 3) to the main hydraulic pump (M) and then to the main control valve (E).

From the main control valve, approximately 4-3/4 gallons (18 L) of oil flows through a flow control plug in the valve and ovor to the secondary control valve (K. Fig. 3). The balance of the oil from the main control valve is then returned to the reservoir (I).

The secondary control valve (K. Fig 3) then directs the 4-3/4 gallons (18 L) of oil to the auto header valve (L). where it flows through the valve and back to the reservoir (I). 

GENERAL INFORMATION—Continued

MAIN CONTROL VALVE

GENERAL INFORMATION Height Control Activated

The automatic header height control hydraulic system obtains oil Irom the flow control plug in the main control valve. This same oil is also used to swing the unloading auger

Height Control Not Activated

SECONDARY CONTROL VALVE

GENERAL INFORMATION

AUTO HEADER VALVE

GENERAL INFORMATION—Continued

DROP RATE VALVE

GENERAL INFORMATION

The drop rate valve controls the rate of drop of tho header. The drop rate valve affects the rate of drop, only for automatic header height control.

Header Raising

Group 25

DIAL-A-MATIC HEADER HEIGHT CONTROL GENERAL INFORMATION, DIAGNOSIS, AND TESTS

GENERAL INFORMATION—Continued

Hydraulic System

The hydraulic system consists of the flow control plug in the main control valve (B) (Fig. 1), secondary control valve (D), auto header valve (F). drop rate valve (C), header lift cylinders (A), and oil cooler (7720 and 8820). When the auto header valve is activated, the hydraulic system raises or lowers the header,

NOTE: Information covering the electrical and hydraulic systems (or Dial-A-Matic header height control has been separated from the main electrical system (Section 240) and hydraulic systems (Section 270), and is included in this section.

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