prjctx.net

Fan Runs Continuously

Monitor

Fan Runs Continuously means the cooling system or fan-control circuit may not be controlling engine temperature correctly. Cooling problems can overheat the engine, especially at idle or in traffic.

Monitor closely — watch for other symptoms developing.

Check These First

Before diving into diagnosis, quickly verify these:

  • 1Check whether the engine is actually hot.
  • 2See if the fan stays on after the key is off and drains the battery.
  • 3Check coolant level when cold.
  • 4Scan for coolant temperature sensor or fan-control codes.

Most Likely Causes

Ranked from most to least common — start at the top.

1

Engine Coolant Temperature Sensor Fault

Engine Coolant Temperature Sensor Fault means the computer may be receiving a false coolant-temperature reading It can cause overheating, fan warnings, AC performance problems, or intermittent fan operation depending on the vehicle.

Fix SoonDIY ModerateMost likely: Failed fan motor, relay, fuse, or control module →
2

Stuck Cooling Fan Relay

Stuck Cooling Fan Relay means the fan relay is stuck closed and keeps the fan running after it should shut off It can cause overheating, fan warnings, AC performance problems, or intermittent fan operation depending on the vehicle.

MonitorDIY ModerateMost likely: Failed fan motor, relay, fuse, or control module →
3

AC Pressure Sensor Fault

An AC pressure sensor fault means the HVAC control system may be receiving an incorrect refrigerant-pressure signal. On many vehicles that signal can affect compressor operation and cooling fan command, so the fan may run constantly, fail to run correctly, or the AC may stop cooling.

MonitorDIY ModerateMost likely: Failed AC pressure sensor or transducer →
4

Cooling System Overheating

Cooling System Overheating means engine temperature is high enough that the fan may be running constantly or the vehicle may be near overheating It can cause overheating, fan warnings, AC performance problems, or intermittent fan operation depending on the vehicle.

Stop DrivingDIY ModerateMost likely: Failed fan motor, relay, fuse, or control module →
5

Cooling Fan Control Module Fault

Cooling Fan Control Module Fault means the electronic module controlling fan speed or fan command is not switching the fan correctly It can cause overheating, fan warnings, AC performance problems, or intermittent fan operation depending on the vehicle.

Fix SoonShop JobMost likely: Failed fan motor, relay, fuse, or control module →

Related Symptoms in Cooling

Other problems to check if this isn't your issue.

Coolant Disappearing With No Visible Leak

Fix Soon

Coolant disappearing without a puddle means the leak may only happen under pressure, may evaporate on hot parts, may leak inside the cabin through the heater core, or may be entering the engine. This needs diagnosis because low coolant can quickly lead to overheating.

Coolant Leak

Fix Soon

A coolant leak means the cooling system is losing the fluid that carries heat away from the engine. Small leaks can become major leaks fast. Low coolant can cause overheating, no cabin heat, head gasket damage, or engine failure.

Cooling Fan Not Working

Fix Soon

Cooling Fan Not Working needs a focused diagnosis because the same symptom can come from several different parts. Start with the checks that match when it happens, then verify the likely cause before replacing parts.

Radiator Problems

Fix Soon

Radiator component malfunction affecting heat dissipation.

Thermostat and Coolant Flow Diagnosis

Fix Soon

A hub for thermostat behavior, housing leaks, stuck-open running cold, and stuck-closed overheating.