What is Komatsu PC210-8 Fault Code DA25KP?

Fault Code DA25KP indicates a malfunction in the air conditioner compressor clutch relay circuit within the Komatsu PC210-8 excavator's electrical system. This code is triggered when the Engine Control Module (ECM) detects abnormal voltage or current flow in the A/C compressor clutch relay control circuit, preventing proper engagement or disengagement of the air conditioning compressor.

This specific code affects the operator comfort system but can also impact engine performance indirectly. When the ECM cannot properly control the A/C compressor clutch, it may prevent the compressor from engaging entirely or cause erratic cycling. On the PC210-8, the climate control system is integrated with the cab's electrical network, and relay failures can sometimes create parasitic electrical drains or trigger additional diagnostic trouble codes. While not immediately critical to hydraulic or engine operation, ignoring this fault can lead to increased electrical system stress and reduced operator productivity during hot weather conditions.

Common Symptoms

• Air conditioning system fails to engage or blows warm air continuously despite controls being activated
• Intermittent A/C operation where cooling cycles on and off unexpectedly, particularly during high engine loads
• Warning indicator on the monitor panel displaying the fault code DA25KP with possible amber caution light
• Unusual clicking sounds from the relay panel area behind the operator's seat when attempting to activate A/C
• Increased engine idle fluctuation when A/C switch is toggled due to improper compressor load management

Potential Causes

The most common causes for DA25KP in used PC210-8 excavators include:

• Failed A/C compressor clutch relay located in the main relay panel, often due to contact wear or coil failure after years of thermal cycling
• Damaged wiring harness between the ECM and relay panel, particularly at known rub points near the cab mounting brackets where vibration causes insulation breakdown
• Corroded or loose electrical connectors at the relay socket or ECM connector C3, especially in machines operated in humid or coastal environments
• Faulty A/C compressor clutch coil creating excessive resistance or an open circuit that prevents relay energization
• ECM internal driver circuit failure affecting the relay control output (less common but documented in older PC210-8 units)
• Blown fuse F7 (15A) in the main fuse box protecting the A/C circuit

How to Troubleshoot and Fix Code DA25KP

Step 1: Initial Inspection and Code Verification Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to verify DA25KP is active. Check the A/C operation manually—toggle the A/C switch while monitoring if the compressor clutch engages (listen for click and observe clutch pulley). On used excavators, visually inspect the relay panel behind the operator seat for signs of water intrusion, corrosion, or burnt relay sockets.

Step 2: Relay and Fuse Testing Locate the A/C compressor clutch relay in the main relay panel (consult service manual for exact position—typically labeled "A/C COMP"). Remove the relay and inspect terminals for corrosion or heat damage. Using a multimeter, test relay coil resistance (should read 70-90 ohms) and verify continuity between switched contacts. Check fuse F7 for continuity. Swap the A/C relay with an identical relay (such as the fuel pump relay) to determine if the fault follows the relay.

Step 3: Wiring Harness and Voltage Checks With ignition on but engine off, measure voltage at relay socket terminal 85 (should show battery voltage 12V). Check terminal 86 for ECM ground signal when A/C switch is activated (should drop to near 0V). Inspect harness routing from relay panel to ECM connector C3, particularly checking for harness abrasion against the cab mounting frame—a common wear point on PC210-8 models. Test continuity between relay socket and ECM connector pins (refer to wiring diagram).

Step 4: Compressor Clutch Circuit Testing Disconnect the A/C compressor clutch connector. Measure resistance across clutch coil terminals (typically 3-5 ohms). Check for voltage supply at clutch connector with A/C activated and relay manually bridged—should read 12V. On used machines, examine connector pins for green corrosion (copper oxidation) which creates high resistance.

Step 5: ECM Output Testing and Repair If all previous tests pass, the ECM output driver may be faulty. This requires testing pin voltage at ECM connector C3 (specific pin varies—consult schematic) while commanding A/C engagement through diagnostic software. If no switching occurs, ECM repair or replacement is necessary. For used excavators, always verify all software updates are installed, as Komatsu issued calibration updates addressing relay control timing on early PC210-8 models.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number. Complex electrical diagnostics should be performed by certified Komatsu technicians with proper diagnostic equipment to prevent further damage.