Fuses and relays: Difference between revisions
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Because Fieros were offered with different engines, trim levels, and options, the exact downstream loads can vary by year and equipment. The fuse-block labels themselves are usually the most useful starting point for diagnosis. | Because Fieros were offered with different engines, trim levels, and options, the exact downstream loads can vary by year and equipment. The fuse-block labels themselves are usually the most useful starting point for diagnosis. | ||
== Power distribution and fusible links == | |||
The fuse block is only one part of the Fiero power distribution system. | |||
The 1988 service manual describes the power distribution system as including: | |||
* Fusible links | |||
* Fuses | |||
* Circuit breakers | |||
* Light switch | |||
* Ignition switch | |||
Fusible links are short protective wire sections used on higher-current feed circuits. They are intended to melt and stop current flow if excessive current occurs in a part of the electrical system that is not protected by ordinary fuses or circuit breakers. | |||
Fusible links should not be replaced with ordinary wire. | |||
The 1988 service manual lists several fusible-link locations, including fusible links at the battery junction block, forward lamp harness, starter solenoid, and rear bulkhead connector. Exact fusible-link identification should be checked against the correct model-year wiring diagram. | |||
Related topics: | |||
* [[Electrical system]] | |||
* [[Wiring diagrams]] | |||
* [[Connector pinouts]] | |||
== Rear fuse-block connectors == | == Rear fuse-block connectors == | ||
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== Flasher and relay locations == | == Flasher and relay locations == | ||
The owner's manual identifies | The fuse block protects many circuits, but several flashers and relays are located elsewhere. | ||
The owner's manual identifies these under-dash locations: | |||
* The hazard flasher and horn relay are located under the right side of the instrument panel. | * The hazard flasher and horn relay are located under the right side of the instrument panel. | ||
* The turn-signal flasher is located on the left side of the steering column, under the instrument panel. | * The turn-signal flasher is located on the left side of the steering column, under the instrument panel. | ||
The 1988 service manual gives additional component locations, including: | |||
* Fuse block — behind the left side of the instrument panel | |||
* Coolant fan relay — left front corner of the front compartment | |||
* Fuel pump relay — engine compartment, left side of the rear bulkhead | |||
* A/C power relay — front compartment, on the right side of the heater/A/C module | |||
* High-speed blower relay — on the right side of the heater/A/C plenum | |||
These locations are useful starting points, but relay locations and wiring details should still be verified against the correct model-year wiring diagram. | |||
Related topics: | Related topics: | ||
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* [[Headlight control module]] | * [[Headlight control module]] | ||
* [[Horn]] | * [[Horn]] | ||
* [[Air conditioning]] | |||
== What the common abbreviations mean == | == What the common abbreviations mean == | ||
Revision as of 23:20, 18 July 2026
Fuses and relays refers to the fuse block, fuses, circuit breakers, fusible links, and relay-controlled circuits used in the Pontiac Fiero electrical system.
On the Fiero, many electrical problems can be traced to a blown fuse, poor fuse-block contact, a failed circuit breaker, a bad ground, damaged wiring, or a failed relay in a specific circuit.
Fuse access location
The main fuse block is located under the left side of the instrument panel, on the driver's side.
Access to the fuses is through a fuse-block access door under the left side of the dash. The access door is released by pushing inward on the two release tabs near the center and swinging the door down toward the seat.
This location makes the fuse block accessible from the driver's footwell area.
Fuse block layout
The Fiero fuse block contains standard blade fuses and circuit breakers.
The fuse block includes circuits for engine control, fuel pump, lighting, heater and air conditioning, turn signals, brake lights, power windows, gauges, wipers, radio, courtesy lighting, and power accessories.
Because fuse labels are abbreviated, the fuse list below expands the labels into their common circuit meanings.
Fuse list
The fuse-block labels most commonly shown for the Fiero are:
| Fuse / breaker label | Rating | Common meaning / circuit | Notes |
|---|---|---|---|
| ECM IGN | 10A | ECM / Computer Command Control ignition feed | Engine-control ignition power |
| F PUMP | 10A | Fuel pump relay / oil pressure switch feed | Fuel pump circuit |
| TAIL | 20A | Tail lamps, parking lamps, side marker lamps, license plate lamp, and related illumination | Exterior running lights and related illumination |
| FAN E | 20A | Coolant fan relay coil; engine/trunk blower on earlier V6 cars where equipped | Cooling fan control circuit; verify by model year |
| TURN B/U | 20A | Turn-signal flasher and backup lamps | Signal / reverse-light related |
| TBI INJ1 | 5A | Throttle-body injection injector circuit 1 | Four-cylinder engine-control related |
| STOP HAZ | 20A | Stop lamps, hazard flasher, and warning chime | Brake-light / hazard circuit |
| HTR/A/C | 25A | Heater / air-conditioning circuit | HVAC-related power |
| GAUGES | 10A | Gauges and related warning/control circuits | Instrument-related circuits |
| TBI INJ2 | 5A | Throttle-body injection injector circuit 2 | Four-cylinder engine-control related |
| BAT | 20A | Battery-fed circuit | Constant-power feed for related circuits |
| WDO | 30A circuit breaker | Power windows | Power-window protection |
| INST LP | 5A | Instrument panel lamps and headlight warning | Dash lighting / warning circuit |
| RADIO | 10A | Radio and related control circuits | Radio, cruise control, VSS/TCC-related circuits depending on equipment |
| PWR ACC | 30A circuit breaker | Power door locks and rear window defogger | Power accessory circuit |
| WIPER | 25A | Windshield wiper circuit | Wiper motor / related circuit |
| CTSY/LID | 25A | Courtesy lights, rear compartment light, rear lock relay, and power sport mirror control | Interior courtesy / rear compartment / power mirror-related circuit |
Because Fieros were offered with different engines, trim levels, and options, the exact downstream loads can vary by year and equipment. The fuse-block labels themselves are usually the most useful starting point for diagnosis.
Power distribution and fusible links
The fuse block is only one part of the Fiero power distribution system.
The 1988 service manual describes the power distribution system as including:
- Fusible links
- Fuses
- Circuit breakers
- Light switch
- Ignition switch
Fusible links are short protective wire sections used on higher-current feed circuits. They are intended to melt and stop current flow if excessive current occurs in a part of the electrical system that is not protected by ordinary fuses or circuit breakers.
Fusible links should not be replaced with ordinary wire.
The 1988 service manual lists several fusible-link locations, including fusible links at the battery junction block, forward lamp harness, starter solenoid, and rear bulkhead connector. Exact fusible-link identification should be checked against the correct model-year wiring diagram.
Related topics:
Rear fuse-block connectors
The rear-view diagram shows connector cavity locations at the back of the fuse block.
The two brown rear connector locations are marked:
- IGN
- LP
These should be checked if there is evidence of heat damage, loose connections, poor previous repairs, or intermittent power loss through the fuse block.
Circuit breakers
The Fiero fuse block also uses circuit breakers.
The most obvious ones shown in the diagram are:
- WDO – 30A circuit breaker for the power-window circuit
- PWR ACC – 30A circuit breaker for power-accessory circuits
Unlike an ordinary fuse, a circuit breaker may reset after cooling, depending on type. This can cause an intermittent fault.
Flasher and relay locations
The fuse block protects many circuits, but several flashers and relays are located elsewhere.
The owner's manual identifies these under-dash locations:
- The hazard flasher and horn relay are located under the right side of the instrument panel.
- The turn-signal flasher is located on the left side of the steering column, under the instrument panel.
The 1988 service manual gives additional component locations, including:
- Fuse block — behind the left side of the instrument panel
- Coolant fan relay — left front corner of the front compartment
- Fuel pump relay — engine compartment, left side of the rear bulkhead
- A/C power relay — front compartment, on the right side of the heater/A/C module
- High-speed blower relay — on the right side of the heater/A/C plenum
These locations are useful starting points, but relay locations and wiring details should still be verified against the correct model-year wiring diagram.
Related topics:
What the common abbreviations mean
Some Fiero fuse-block abbreviations are not immediately obvious:
| Abbreviation | Meaning |
|---|---|
| ECM IGN | Engine Control Module ignition feed |
| F PUMP | Fuel pump |
| HTR/A/C | Heater / air conditioning |
| TURN B/U | Turn signals / backup lamps |
| TBI INJ1 / INJ2 | Throttle-body injection injector circuits |
| STOP HAZ | Stop lamps / hazards |
| WDO | Power windows |
| INST LP | Instrument lamps |
| CTSY/LID | Courtesy / decklid circuit |
Relay-controlled circuits
The fuse block protects many circuits, but the actual relay for a circuit may be located somewhere else in the car.
Important relay-controlled circuits include:
For some circuits, the fuse in the fuse block protects the control or supply side, while the actual load is switched by a relay located elsewhere in the car.
Examples:
- The F/PMP fuse is part of the fuel-pump circuit, but the actual pump is also controlled by the fuel-pump relay and oil-pressure-switch backup circuit.
- The HTR/A/C circuit is related to HVAC operation, but A/C and radiator-fan operation may also involve relays.
- The headlight system differs between 1984-1986 and 1987-1988 Fieros and should be diagnosed using the correct year-specific system information.
Related topics:
Common fuse-block problems
Common Fiero fuse and fuse-block problems include:
- Blown fuse
- Fuse installed with the wrong amperage
- Poor contact between fuse and fuse-block terminals
- Corrosion
- Heat damage
- Previous-owner wiring modifications
- Loose rear connector cavities
- Circuit breaker failure
- Repeatedly blown fuse caused by a short or failed component
A blown fuse should not simply be replaced repeatedly without finding the cause.
Diagnosis
When diagnosing a Fiero fuse or relay-related electrical problem:
- Identify the affected circuit.
- Check the correct fuse or circuit breaker.
- Verify the fuse rating.
- Check for power on both sides of the fuse.
- Inspect the fuse-block terminals for corrosion or looseness.
- Check the rear connector cavities if there is evidence of heat or intermittent power loss.
- If the circuit also uses a relay, test that relay and the related wiring.
- Inspect grounds.
- Inspect for aftermarket wiring or previous repairs.
A fuse that looks good visually may still have poor contact or may not be receiving power.
Repeatedly blown fuses
A fuse that blows repeatedly indicates a fault somewhere in the circuit.
Possible causes include:
- Short to ground
- Pinched or chafed wiring
- Failed motor
- Failed relay
- Failed switch
- Incorrect bulb or component
- Water intrusion
- Poor aftermarket wiring
Do not solve a repeatedly blown fuse by installing a higher-rated fuse.
Notes
This page is mainly a Fiero fuse-block overview.
For detailed circuit diagnosis, it is often better to continue to the specific circuit page, such as: