This instruction show guide on how to perform CASE IH 20 series Axial-Flow combine low pressure standby.This test is used to determine low-pressure standby.There are two items responsible for low pressure standby,the 375-400 PSI (26-28 bar)spring on the flow compensator spool and the 0.078 mm (0 .031 in)orifice in the steering hand pump –which creates back pressure in the signal line of approximately 50-150 psi.The 375-400 PSI (26-28 bar)spring plus the back pressure will equal low-pressure standby.The following test will show the spring setting of the flow compensator spool.
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TEST PROCEDURE
1 Attach a 69 bar (1000 psi)gauge to the signal line pressure test port (14)on the main valve assembly.It is recommended to install a needle valve in the test hose to prevent damage to the gauge.With the needle valve closed,start the engine.At low idle,open the needle valve on the gauge.Make sure that the steering wheel is not moved or that other hydraulic functions are not activated otherwise the gauge could be damaged. The signal line pressure should be approximately 50-150 PSI (3 .45-10.4 bar).Record this number for use later.
2 Then attach the SAME 69 bar (1000 psi)gauge to the PFC pump pressure test port (13) on the main valve assembly.With the needle valve closed,start the engine.At low idle open the needle valve on the gauge.Make sure that the steering wheel is not moved or that other hydraulic functions are not activated otherwise the gauge could be damaged.The PFC pump pressure port should read 375-400 PSI (26-28 bar)above the reading that was recorded from the signal line.
If the PFC pump pressure port does not read 375-400 PSI (26-28 bar)ABOVE the signal line, adjustment of the flow compensator spool spring is required.The adjustment procedure is as follows:
Example Signal line pressure port reading 112 psi (7 .7 bar) Flow compensator spool spring setting +400±25 psi (27 .5 bar
PFC pump pressure port reading AFTER adjustment 512±25 psi (35 .3 bar)
3 Remove the cap for the adjustment screw located on the compensator.
4 Loosen the jam nut.
5 Use an allen wrench to adjust the pressure to match the number calculated.(See example.)
6 Tighten the jam nut.Repeat test to verify the low-pressure standby setting.
7 If not correct,make adjustment again.If it is correct,replace the cap.
