Komatsu WA250-3–WA320-3: transmission, ECSS and Active Plus hydraulics

The WA250-3 kick-down switch and ECSS do different jobs

Komatsu's North American WA250-3 booklet describes a countershaft powershift with four ratios in each direction. The thumb switch on the boom lever requests a second-to-first downshift for digging. Selecting reverse then returns it from first to second.

That behavior belongs to the transmission control; it is separate from the optional ECSS suspension system.

ECSS connects accumulators to the boom-cylinder circuit through electrically operated valves. Its job is to absorb pitching when the loader travels with material. A loader may have the kick-down switch without ECSS.

Inspect the suspension controls and equipment before treating a bouncing ride as a fault in an installed accumulator system.

The booklet's engine is the S6D102E-1. It is a turbocharged six-cylinder diesel with a mechanical all-speed governor, and its cold-start preheat duration follows coolant temperature. Match that engine identification before applying an electronic-injection diagnosis from a later WA250 generation.

WA250-3 bucket weight and hydraulic flow need their conditions

The loader pump and steering pump have separate discharge entries. So do their relief settings. Their combined output is not a single attachment flow allowance.

The basic control valve serves boom and bucket, while the third valve and associated piping are listed as optional equipment.

Komatsu's bucket table changes dumping clearance, breakout force and tipping load with the bucket selected. Its standard comparison includes a cab, operator, full fuel, specified tires and additional counterweight. The canopy conversion has its own weight deduction.

Another note forbids using tire ballast with that additional counterweight. Keep those conditions attached to the figures when evaluating a used machine or choosing a material bucket.

Service access is equally specific: the gull-wing covers and rear grille have pneumatic supports, batteries sit near ground level in the counterweight, and the hydraulic tank and transmission case have separate sight gauges. A fluid-level observation should identify which gauge was checked.

Source: Original Komatsu WA250-3 North American booklet, controls, engine, bucket conditions and service access.

WA320-3 Active Plus separates pump switching from work-mode selection

The March 2000 European Active Plus brochure describes APS and AMS as different systems. APS changes the hydraulic supply as resistance rises. At lower pressure, the main and switching pumps work together for faster movement; under heavy digging or lifting resistance, the switching pump disengages and the main pump supplies the higher-pressure stage.

Those two flow entries describe operating stages, not two flows available together at maximum pressure.

AMS is the operator's High, Standard or Economy choice. High retains the two-stage arrangement and later upshifts for loading work. Standard shifts earlier and leaves the switching pump disconnected.

Economy also changes engine management. A complaint about slow implement movement should therefore include the selected mode, not just the accelerator position.

The optional electronic ALS accumulator system reacts to travel speed and gearing to reduce loader pitching. It has a separate purpose from APS. The EDIMOS II monitor also retains error information, so the active warning and stored record are worth distinguishing during an inspection.

This publication identifies the S6D114E-1 engine and a European Active Plus configuration. It is not a universal engine specification for every WA320-3 regional or serial variant. Its standard bucket table excludes extra counterweight and specifies its tires.

The teeth-equipped buckets also have different capacities from their bolt-on-edge equivalents. Keep those details with a quoted tipping load or transport weight.

Source: Komatsu WA320-3 Active Plus VESS074502, March 2000, APS, AMS and equipment conditions.