Radiator fan: Difference between revisions
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The radiator fan is intended to run when coolant temperature becomes high enough that extra airflow through the radiator is needed. | The radiator fan is intended to run when coolant temperature becomes high enough that extra airflow through the radiator is needed. | ||
Fiero fan-control strategy depends on model year, engine, and equipment. | |||
Some systems use a coolant temperature fan switch to operate the radiator fan relay when coolant temperature exceeds approximately 230°F / 110°C. | |||
ECM-controlled systems use the ECM to provide a ground path for the fan relay. In this arrangement, the ECM commands the fan on when coolant temperature is above approximately 108°C / 230°F, and turns the fan off again when coolant temperature drops to about 101°C. | |||
A fan that does not run until a high indicated temperature does not automatically mean the fan system has failed. The factory fan-on temperature is relatively high compared with normal thermostat opening temperature. | A fan that does not run until a high indicated temperature does not automatically mean the fan system has failed. The factory fan-on temperature is relatively high compared with normal thermostat opening temperature. | ||
Because the Fiero temperature gauge, warning light, fan switch, coolant temperature sensor, and ECM control circuit are separate or partly separate depending on year and equipment, diagnosis should use the correct wiring diagram for the specific car. | |||
== Air-conditioning operation == | == Air-conditioning operation == | ||
Revision as of 23:52, 18 July 2026
Radiator fan refers to the electric cooling fan used at the front radiator of the Pontiac Fiero.
The radiator fan helps pull air through the radiator when vehicle speed or natural airflow is not enough to keep coolant temperature under control.
Overview
The Fiero radiator is mounted at the front of the car, while the engine is mounted behind the passenger compartment.
Because of this layout, the cooling system uses long coolant pipes between the engine and the front radiator. The radiator fan is mounted at the radiator and is used to increase airflow through the radiator when needed.
A radiator fan problem can cause overheating, especially at idle, in traffic, in hot weather, during air-conditioning operation, or whenever the car is moving slowly.
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Location
Image wanted: Photo or diagram showing the Fiero radiator fan location at the front radiator, plus the fan shroud, wiring connector, fan relay, and fan switch/control locations if possible.
The radiator fan is mounted at the front radiator.
The radiator itself is located at the front of the car, behind the front fascia area.
The fan motor is attached to the radiator support, and the fan shroud helps direct air through the radiator instead of allowing air to recirculate around the fan.
The fan is part of the front cooling-system assembly, not the engine-compartment assembly.
Function
The radiator fan moves air through the radiator when airflow from vehicle movement is not enough.
The fan is especially important during:
- Idle
- Slow traffic
- Hot weather
- Extended low-speed driving
- Air-conditioning use, if equipped
- Cooling-system diagnosis
On air-conditioned cars, the fan also helps airflow through the A/C condenser.
Fan assembly
The radiator fan assembly includes:
- Fan motor
- Fan blade assembly
- Fan shroud
- Wiring connector
- Mounting hardware
- Related control circuit
The fan must remain balanced. A bent or damaged fan blade assembly should not be repaired and reused. A damaged fan assembly should be replaced, because an out-of-balance fan can fail during operation.
Fan control
Radiator fan control depends on year, engine, and equipment.
Depending on the model year and configuration, fan operation may involve:
- Coolant temperature fan switch
- ECM control
- Radiator fan relay
- Air-conditioning request
- A/C pressure or control circuitry
- Fuse or fusible-link feed
- Ground circuit
- Related wiring and connectors
Because fan-control details vary, diagnosis should use the correct wiring diagram and service information for the specific car.
Related topics:
Temperature-controlled operation
The radiator fan is intended to run when coolant temperature becomes high enough that extra airflow through the radiator is needed.
Fiero fan-control strategy depends on model year, engine, and equipment.
Some systems use a coolant temperature fan switch to operate the radiator fan relay when coolant temperature exceeds approximately 230°F / 110°C.
ECM-controlled systems use the ECM to provide a ground path for the fan relay. In this arrangement, the ECM commands the fan on when coolant temperature is above approximately 108°C / 230°F, and turns the fan off again when coolant temperature drops to about 101°C.
A fan that does not run until a high indicated temperature does not automatically mean the fan system has failed. The factory fan-on temperature is relatively high compared with normal thermostat opening temperature.
Because the Fiero temperature gauge, warning light, fan switch, coolant temperature sensor, and ECM control circuit are separate or partly separate depending on year and equipment, diagnosis should use the correct wiring diagram for the specific car.
Air-conditioning operation
On air-conditioned cars, the radiator fan may run when the air conditioning is selected.
On 1988 ECM-controlled applications, the ECM can turn on the fan when an A/C request is present. The A/C clutch does not necessarily have to be engaged for the fan request to occur.
If the fan works with air conditioning but not from temperature control, the fan motor and part of the relay/wiring circuit may be functional, while the temperature-control side still needs diagnosis.
If the fan does not work with either air conditioning or high coolant temperature, check the fan motor, relay, power feed, ground, wiring, and control circuit.
Coolant sensor failure mode
On 1988 ECM-controlled applications, a coolant sensor failure can cause the ECM to command the cooling fan on continuously.
This may occur when diagnostic trouble Code 14 or Code 15 is set.
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Common symptoms
Possible radiator-fan-related symptoms include:
- Engine overheats at idle
- Engine overheats in traffic
- Temperature drops when driving faster
- Fan never turns on
- Fan runs constantly
- Fan works only with air conditioning
- Fan does not work with air conditioning
- Fan fuse or relay problem
- Intermittent overheating
- Temperature gauge rises while stationary
- Fan is noisy, vibrating, or rubbing
- Fan connector or wiring is damaged
Common causes
Common causes of radiator fan problems include:
- Failed fan motor
- Failed fan relay
- Faulty fan switch
- Faulty coolant temperature sensor or control input
- Wiring problem
- Poor connector contact
- Blown fuse
- Fusible-link or power-feed problem
- Poor ground
- Air-conditioning control issue
- ECM or control-circuit issue, depending on year
- Previous wiring modifications
- Damaged or out-of-balance fan assembly
Diagnosis
Basic diagnostic checks include:
- Confirm whether the engine is actually overheating.
- Check coolant level and cooling-system condition.
- Check whether the fan turns freely.
- Inspect the fan blade and shroud.
- Check whether the fan runs when commanded or powered according to the correct test procedure.
- Check the fan fuse, fusible-link feed, or power supply as applicable.
- Check the fan relay.
- Inspect fan wiring and connectors.
- Check fan ground.
- Check the fan switch, coolant temperature sensor, or control circuit as applicable.
- Check whether the fan operates with air conditioning if equipped.
- Check the correct wiring diagram for the year, engine, and configuration.
Do not replace the fan motor before checking the relay, power feed, ground, and control circuit.
Actual overheating versus gauge indication
Before diagnosing the fan circuit, determine whether the engine is actually overheating.
A temperature gauge or warning light can indicate overheating even if the engine is not boiling over. Gauge accuracy, sender operation, wiring, and instrument-panel problems can affect the reading.
If available, compare the indicated temperature with ECM coolant temperature data or another reliable temperature check.
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Relationship to overheating
A radiator fan problem often shows up most clearly when the car is stopped or moving slowly.
If the car cools normally at road speed but overheats at idle or in traffic, the radiator fan system should be checked.
However, overheating can also be caused by:
- Trapped air
- Low coolant
- Crushed coolant pipes
- Restricted radiator
- Incorrect or faulty radiator cap
- Incorrect or faulty thermostat
- Water pump problem
- Collapsed hose
- Poor coolant flow
- Incorrect coolant filling procedure
- Temperature gauge or sender problem
Related topics:
Relationship to the radiator fan relay
The radiator fan motor is not normally powered directly by the temperature switch or ECM.
The fan relay handles the fan motor current. The switch or ECM controls the relay side of the circuit.
A failed relay, poor relay connection, missing power feed, or bad relay ground/control circuit can prevent the fan from running even if the fan motor itself is good.
Related topic:
Relationship to the radiator fan switch
Some Fiero fan-control systems use a coolant temperature fan switch to control the relay.
The fan switch should not be confused with the temperature gauge sender or warning-light switch. These can be separate components with different functions.
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Manual fan switches
Some owners add a manual fan switch to turn the radiator fan on from inside the car.
A manual switch may be useful as a diagnostic aid or temporary backup, but it should not be used to hide an unresolved cooling-system or fan-control problem.
If a manual fan switch is installed, it should be wired safely through the relay/control side of the circuit and should not bypass proper fuse protection.
For a stock car, the original fan-control circuit should normally be diagnosed and repaired rather than bypassed.
Service notes
When working on the radiator fan system:
- Keep hands, tools, wiring, and clothing away from the fan.
- The fan may start unexpectedly if commanded by the control circuit.
- Do not reuse a bent or damaged fan blade assembly.
- Check fan operation with the correct model-year procedure.
- Check the relay and wiring before replacing the fan motor.
- Verify whether the car uses switch-controlled or ECM-controlled fan logic.
- Verify whether the car has air conditioning.
- Do not assume every overheating problem is caused by the fan.
- Do not assume the gauge is accurate without checking if symptoms do not match.
Notes
Do not assume the radiator fan is working just because the engine overheats slowly rather than immediately.
The fan should be tested directly if overheating occurs at idle, in traffic, or during low-speed operation.
Also do not assume every overheating problem is caused by the fan. The Fiero cooling system must be properly filled and free of trapped air.