Case IH 2844 (785.07) - DEC – DEC: HST - overload

The fault code indicates a Hydrostatic Transmission (HST) overload. This condition occurs when the hydrostatic transmission experiences excessive load, causing the main relief valve to activate. When activated, oil in the high-pressure circuit is bypassed to the low-pressure circuit to prevent internal damage to the transmission. While this can be a legitimate mechanical overload, it is frequently triggered by false signals due to low/degraded hydraulic fluid, restricted hydraulic filters, or a faulty range/neutral switch in the pedal circuit.

• VESTRUM CVX
• Compact Farmall Series (35A, 40A, 35C, 40C, 45C, 50C)
• Puma CVX
• Optum CVX
• Self-Propelled Windrowers (WD1904, 8825HP)

1. 1

   Check hydraulic fluid level and condition for low or degraded fluid.

2. 2

   Inspect hydraulic filters for restrictions that could create cavitation or weak hydrostatic performance.

3. 3

   Inspect HST pedal linkage for binding, debris, or bent components preventing return to neutral.

4. 4

   Check the steering column range switch and HST neutral position switch for electrical faults.

5. 5

   Monitor hydraulic oil temperature and charge pressure stability under load using a diagnostic tool.

6. 6

   Test the main relief valve to ensure it is not stuck open or failing prematurely (standard setting on compacts is often around 350 kgf/cm2 / 34.3 MPa).

1. 1

   Fluid and Filter Service

   If the fluid is low or degraded, drain the system and replace the hydrostatic transmission filters. Refill with manufacturer-approved hydraulic fluid.

2. 2

   Clean Electrical Connections

   Unplug the HST control connectors (specifically the range selection switch and pedal circuit switches). Clean them with electrical contact cleaner and reseat them.

3. 3

   Relief Valve Inspection/Replacement

   If the transmission still drops into limp/turtle mode or logs the overload code, remove the side covers to access the transmission release/relief valve. Inspect the valve and O-rings for erosion or damage. Replace the relief valve cartridge or seals if necessary.

4. 4

   Clear Fault Codes

   Use the Case IH Electronic Service Tool (EST) laptop to clear the inactive codes from the DEC memory. On some instrument clusters (ICU2), you may be able to navigate the menu and clear codes using the INCR and DECR keys, depending on the software version.

5. 5

   Recalibrate the DEC

   Perform a DEC transmission calibration procedure to relearn the pedal and valve parameters.