Radiator fan relay
Radiator fan relay refers to the electrical relay used to switch power to the Pontiac Fiero Radiator fan.
The radiator fan relay allows a low-current control circuit to turn on the higher-current radiator fan motor.
Overview
The radiator fan motor requires more current than a simple temperature switch, ECM output, or control circuit should carry directly.
The radiator fan relay acts as an electrical switch. When the control side of the relay is activated, the relay closes and sends power to the radiator fan motor.
A faulty relay, poor connector, wiring problem, blown fuse or fusible link, bad ground, failed fan motor, or control-circuit problem can prevent the radiator fan from operating correctly.
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Location
Image wanted: Photo or diagram showing the radiator fan relay location near the left front corner of the Fiero front compartment.
The radiator fan relay is located in the front compartment area, near the front cooling-fan and radiator wiring.
Factory service information identifies the coolant fan relay location as the left front corner of the front compartment.
The exact relay appearance, bracket, connector position, and wiring should be checked against the correct model-year wiring diagram and the actual car.
The radiator fan relay should not be confused with the Radiator fan switch. The switch or ECM control circuit triggers fan operation; the relay switches power to the fan motor.
Function
The radiator fan relay switches power to the fan motor.
A simplified fan-control path is:
- The engine reaches the fan-control temperature, the air conditioning requests fan operation, or another fan-control condition is met.
- The fan-control circuit activates the relay.
- The relay closes.
- Power is sent to the radiator fan motor.
- The radiator fan runs.
The relay allows the fan motor to receive the current it needs without routing all fan-motor current through the temperature switch, ECM, or control circuit.
Power side and control side
The radiator fan relay has two basic sides:
- A high-current power side for the fan motor
- A low-current control side used to energize the relay
The power side carries fan-motor current.
The control side may be triggered by a coolant temperature switch, ECM control, air-conditioning request, or related wiring depending on year and equipment.
A relay can click even if the fan motor does not run. In that case, the control side may be working, while the power side, fan motor, fan ground, connector, or power feed may still have a problem.
Fan-control systems
Fiero fan-control strategy depends on model year, engine, and equipment.
Depending on the car, radiator fan relay operation may involve:
- Coolant temperature fan switch
- ECM control
- Air-conditioning request
- A/C pressure or control circuit
- Fuse or fusible-link feed
- Relay power circuit
- Relay ground/control circuit
- Fan motor ground
- Related wiring and connectors
Some systems use a coolant temperature fan switch to operate the relay. ECM-controlled systems use the ECM to provide a ground path for the fan relay.
Because the Fiero fan-control circuit varies by year and equipment, diagnosis should use the correct wiring diagram for the specific car.
ECM-controlled operation
On ECM-controlled fan systems, the ECM can energize the radiator fan relay by completing the relay ground/control circuit.
In this arrangement, the ECM may command fan operation for conditions such as:
- High coolant temperature
- Air-conditioning request
- Certain coolant temperature sensor circuit failures
Factory service information for ECM-controlled cooling-fan operation describes the ECM as providing the ground path that energizes the fan relay. In that system, the fan can be commanded on when coolant temperature is above approximately 108°C / 230°F, and the relay is de-energized again when coolant temperature drops to about 101°C.
This should not be assumed to describe every Fiero fan-control circuit. Earlier or different systems may use a temperature switch or other control path.
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Air-conditioning relationship
On air-conditioned cars, the radiator fan may run when the air conditioning is selected.
On ECM-controlled systems, an A/C request signal can cause the ECM to energize the cooling fan relay. The A/C clutch does not necessarily have to engage for the fan request to occur.
Other fan-control arrangements may use different A/C request or pressure-switch logic, depending on year and equipment.
If the fan works with air conditioning but not from temperature control, the fan motor and part of the relay 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.
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Relationship to the radiator fan switch
The Radiator fan switch is a temperature-controlled switch used on some Fiero fan-control systems.
The radiator fan relay is the electrical power-switching device used to operate the fan motor.
The switch or control circuit activates the relay.
The relay powers the fan.
The radiator fan switch should not be confused with the temperature gauge sender, warning-light switch, coolant temperature sensor, or fan relay. These parts may have separate functions depending on year and equipment.
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Relationship to the fan motor
The relay is part of the fan motor power circuit.
If the relay is commanded on but the fan does not run, the problem may be in:
- Relay contacts
- Fan motor
- Fan ground
- Power feed
- Fan connector
- Relay connector
- Wiring between relay and fan motor
If the fan motor runs when powered directly but not through the car's wiring, the relay circuit, control circuit, power feed, or ground should be checked.
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Common symptoms
Possible radiator-fan-relay-related symptoms include:
- Radiator fan does not turn on
- Fan works intermittently
- Fan works only when jumped or powered directly
- Fan works with one control method but not another
- Engine overheats at idle or in traffic
- Relay clicks but fan does not run
- Relay does not click when fan should be commanded
- Fan runs constantly if relay contacts stick closed
- Melted, loose, corroded, or damaged relay connector
- Fan operates when the relay is tapped or moved
Common causes
Common causes of fan-relay-related problems include:
- Failed radiator fan relay
- Poor relay connector contact
- Corroded terminals
- Broken wiring
- Blown fuse
- Fusible-link or power-feed problem
- Poor fan ground
- Failed fan motor
- Faulty radiator fan switch
- Faulty coolant temperature sensor or control input
- ECM or control-circuit problem, depending on year
- Air-conditioning request or pressure-switch issue
- Previous wiring modifications
Diagnosis
Basic diagnostic checks include:
- Confirm whether the engine is actually overheating.
- Check whether the radiator fan turns freely.
- Check whether the fan motor runs when powered according to the correct test procedure.
- Check the fan fuse, fusible-link feed, or related power supply.
- Inspect the radiator fan relay connector.
- Check for corrosion, heat damage, looseness, or poor contact.
- Listen or feel for relay operation when the fan is commanded.
- Test or substitute the relay if appropriate.
- Check whether power is present at the relay power terminal.
- Check whether the relay control side is being commanded.
- Check the fan motor ground.
- Check the radiator fan switch, ECM control, A/C request, or other control circuit as applicable.
- Check the wiring diagram for the specific year, engine, and configuration.
Do not replace the relay before checking whether the fan motor, power feed, ground, and control circuit are capable of operating.
Relay clicks but fan does not run
If the relay clicks but the fan does not run, the relay control side may be working.
Possible causes include:
- Burned or failed relay contacts
- No power feed to the relay
- Poor relay connector contact
- Open wiring between relay and fan motor
- Failed fan motor
- Poor fan ground
- Damaged fan connector
- High resistance in the fan-motor circuit
A clicking relay does not prove the fan motor is receiving full power.
Relay does not click
If the relay does not click when the fan should be commanded, possible causes include:
- No ignition or control-side feed, depending on circuit
- No relay ground/control signal
- Faulty radiator fan switch
- ECM control issue, where applicable
- Coolant temperature sensor or control-input problem, where applicable
- A/C request problem, where applicable
- Open wiring
- Poor connector contact
- Failed relay coil
The correct wiring diagram should be used to determine whether the relay is controlled by a switch, ECM, A/C circuit, or combination of inputs.
Fan runs constantly
A radiator fan that runs constantly may be caused by:
- Relay contacts stuck closed
- Control circuit shorted to ground
- Manual fan-switch modification
- ECM command due to coolant sensor circuit failure, where applicable
- Incorrect wiring modification
- A/C request or control issue, depending on system
On ECM-controlled systems, certain coolant temperature sensor circuit failures can cause commanded fan operation.
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Relationship to overheating
A failed radiator fan relay can cause overheating at idle, in traffic, or during low-speed operation.
If the car cools normally at road speed but overheats when stationary, the radiator fan circuit should be checked.
However, overheating can also be caused by:
- Low coolant
- Trapped air
- Crushed coolant pipes
- Restricted radiator
- Incorrect or faulty caps
- Thermostat problem
- Water pump problem
- Collapsed hose
- Temperature gauge or sender problem
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Manual fan switches
Some owners add a manual fan switch to control the radiator fan from inside the car.
A manual fan switch should normally be wired through the relay control side rather than carrying fan-motor current directly.
A manual switch should not bypass proper fuse or fusible-link protection.
Manual fan control may be useful as a diagnostic aid or temporary backup, but it should not be used to hide an unresolved cooling-system, relay, fan, or control-circuit fault.
Service notes
When working on the radiator fan relay circuit:
- Keep hands, tools, wiring, and clothing away from the fan.
- The fan may start unexpectedly if commanded by the control circuit.
- Check the fan motor before condemning the relay.
- Check the relay connector for corrosion, looseness, heat damage, or pushed-out terminals.
- Check both the relay power side and relay control side.
- Verify whether the car uses switch-controlled or ECM-controlled fan logic.
- Verify whether the car has air conditioning.
- Use the correct wiring diagram for the model year and equipment.
- Do not assume every overheating problem is caused by the relay.
Notes
Do not assume the fan relay is bad simply because the fan does not run.
The fan motor, fan switch, fuse or fusible link, wiring, ground, relay connector, and control circuit should all be considered.
The relay is separate from the engine-mounted temperature switch or coolant sensor.