Kaeser K004: Kaeser ASD/BS Series Error Code K004

Symptoms

Cooling fan motor thermal overload or failure detected. The fan does not start or stalls during operation, causing rising oil and discharge temperatures.

Possible Causes

Fan motor winding insulation degraded from moisture or high ambient temperature
Fan blade obstructed by debris, wire, or a displaced service tool left in the cowling
Fan motor capacitor failed (for single-phase fan motors) or three-phase supply imbalance
Fan motor bearing seized from lack of grease or contamination

Troubleshooting Steps

Step 1: Attempt to rotate the fan blade by hand with power locked out - it should spin freely with slight bearing drag
If blade is stuck, inspect for physical obstruction and remove any foreign object
Step 2: For capacitor-start fans, disconnect the capacitor and measure capacitance with a multimeter
Replace the capacitor if value is >10% below the nameplate rating (typically 4-10 uF)
Step 3: Measure the three-phase supply voltage at the fan contactor - all phases must be within 5% of nominal
If voltage imbalance exceeds 5%, inspect supply wiring and contactor contacts for pitting
Step 4: Test motor winding insulation with a 500V megohmmeter - expect >10 Mohm to ground
If insulation is <2 Mohm, replace the motor; moisture ingress or varnish breakdown is the likely cause

How to Reset

Reset: Clear the fan fault, verify the fan runs for 60 seconds without tripping, then press Alarm Acknowledge. The temperature alarms will auto-clear once cooling is restored.

Common Replacement Parts

6.2005.0: Cooling fan motor, ASD 40-50 (0.75 kW, 4-pole, 400V 3-phase, IP55)
6.2006.0: Fan blade, 400 mm diameter (Glass-reinforced nylon, 5-blade, clockwise)
6.2007.0: Fan motor capacitor, 6 uF (450V AC, snap-in terminal, for single-phase variant)

Frequently Asked Questions

Q: Can the compressor run without the cooling fan?
No. The fan is essential for oil cooler heat rejection. Running without it will trigger a high-temperature shutdown within 3-5 minutes at full load.
Q: Why does the fan motor fail repeatedly?
Check for voltage spikes from the VSD or contactor chattering. Install an RC snubber or varistor across the contactor coil if switching transients are suspected.

Kaeser ASD/BS Series Error Code K004