Kubota RTV 900 Cooling Fan Relay Location

The Kubota RTV 900 uses an electric cooling fan with a relay that controls power to the fan. Locating the relay is crucial for testing, replacement, or electrical troubleshooting. This guide provides practical, step-by-step instructions to find the cooling fan relay on a Kubota RTV 900, along with tips for safe handling and common issues to check during inspection.

Overview Of The Cooling System And Relay

The RTV 900’s cooling system relies on an electric fan to pull air through the radiator when the engine reaches higher temperatures. The fan is driven by a 12-volt electrical circuit that includes a relay, a fuse, and wiring harnesses. The relay acts as a switch controlled by the engine cooling temperature switch or engine control logic, allowing higher current to flow to the fan without routing it through the ignition switch or control module.

Where The Relay Is Typically Located

In the Kubota RTV 900, the cooling fan relay is usually located in one of the following areas:

• Engine Compartment Fuse/Relay Box: A common spot is a compact fuse/relay box mounted on the left or right side of the engine bay. The box houses multiple relays and fuses, including the cooling fan relay.
• Under the Dash/Instrument Panel: Some RTV 900 models route the relay to a interior fuse/relay panel behind the dash near the steering column.
• Proximity To Radiator And Fan Assembly: In certain builds, the relay sits adjacent to the radiator shroud or the fan assembly for shorter wiring runs.

Because Kubota may update component layouts across model years or regions, exact labeling on the relay box can vary. Look for a 4- or 5-pin relay labeled “FAN,” “COOLING FAN,” or a similar designation in the appropriate fuse box.

How To Locate The Relay On Your RTV 900

• Safety First: Park on a flat surface, turn off the engine, remove the key, and disconnect the negative battery terminal before working on electrical components.
• Access The Engine Bay: Open the hood and look for the radiator, cooling fan, and adjacent wiring harnesses. If there is a side panel, remove it to access the fuse/relay box.
• Inspect The Fuse/Relay Box: Open the box and identify the relays. Check the labeling on the lid or the underside of the cover for “FAN” or “COOLING.”
• Trace The Fan Wiring: Follow the wires from the cooling fan back toward the fuse box. The relay will be in-line within this circuit, usually a small rectangular component with multiple prongs.
• Use The Diagram: If available, consult the RTV 900’s service manual for the wiring diagram that corresponds to your year/model. The diagram will identify the exact pin configuration and relay location.

Verifying The Relay Function

• Visual Inspection: Look for signs of damage, burnt connectors, or loose pins on the relay, fuse, and wiring harness.
• Test With The Relay In Place: With the engine cool, reconnect the battery. Use a multimeter to check for voltage at the fan connector when the thermostat calls for cooling. If power is not present, the relay or the control input may be faulty.
• Relay Rattle Test: With the harness disconnected, lightly tap the relay with a non-conductive tool while the engine attempts to start or reach operating temperature. A temporary fan operation suggests a failing relay.
• Swap Test (If Safe To Do): If another 12V automotive relay of the same rating is available, swap it into the fan circuit to confirm the relay is the issue.

Note: Do not operate the RTV 900 for extended periods with a suspected faulty relay, as the engine can overheat and cause damage.

Common Symptoms Of A Bad Cooling Fan Relay

• The cooling fan fails to turn on at engine high temperatures or when the AC is engaged.
• Fan runs continuously, even after engine cools, indicating the relay is stuck closed.
• Intermittent fan operation or delayed fan activation, suggesting a failing contact inside the relay.
• Burning smell near the fuse box or melted wiring insulation, signaling an electrical fault.

Tools And Steps For Replacing The Relay

• Tools Needed: Screwdrivers, pliers, multimeter, flashlight, replacement 12V automotive relay (check the exact pin count and rating), and electrical contact cleaner.
• Steps:
  1. Disconnect the battery negative terminal to prevent short circuits.
  2. Locate the cooling fan relay as described above.
  3. Remove the relay from its socket by pulling straight out, using a small flat-blade driver if needed.
  4. Compare the replacement relay’s pin configuration to confirm compatibility.
  5. Install the new relay, ensuring a secure seat in the socket.
  6. Reconnect the battery and start the engine to verify that the fan activates at the correct temperature or with the AC engaged.

Wiring Diagram And Wiring sanity Checks

A typical cooling fan relay circuit includes the following connections:

• Power supply from the fuse box to the relay input (12V).
• Relay output to the cooling fan motor.
• Control signal from the temperature switch or engine control unit to the relay coil.
• Ground connection for the relay coil and the fan motor as required by the circuit.

When diagnosing, confirm continuity between the relay pins and verify that the coil receives the control signal when the engine reaches operating temperature. If the control signal is present but the fan remains inactive, suspect the relay or the fan connector for resistance or corrosion.

Maintenance And Preventive Tips

• Inspect electrical connections for corrosion and clean with electrical contact cleaner as needed.
• Replace aging wiring and connectors that show signs of heat damage or fraying.
• Check the radiator cap and coolant level since overheating can cause the cooling system to work harder, increasing electrical load.
• Keep the area around the fuse/relay box free of dirt and moisture to prevent short circuits.