1. Diagnose the Problem:
Before you start replacing parts, you need to pinpoint the source of the fuel gauge malfunction. Is the gauge:
* Completely dead (showing empty all the time)? This suggests a problem with the gauge itself, the sending unit, or the wiring.
* Inaccurate (fluctuating wildly or showing incorrect levels)? This points more towards a faulty sending unit or wiring issues.
* Intermittent (working sometimes, not others)? This again indicates wiring problems, possibly a loose connection or corroded wire.
2. Troubleshooting Steps (in order of likelihood):
* Check the Fuel Level Sending Unit: This is the most common culprit. The sending unit is located in the fuel tank and sends a signal to the gauge. Accessing it requires dropping the fuel tank (a significant undertaking). This involves:
* Safety First: Disconnect the negative battery terminal before starting any work on the fuel system.
* Drain the Fuel Tank: This is crucial for safety and to make the tank lighter to handle.
* Drop the Fuel Tank: Consult a repair manual for your specific Blazer model for detailed instructions. This involves disconnecting fuel lines, electrical connections, and tank straps.
* Inspect the Sending Unit: Look for damage, corrosion, or a broken float arm. Often, a simple cleaning might fix the problem. If damaged, replace the entire sending unit.
* Check the Wiring Harness: Inspect the wiring between the sending unit and the instrument cluster for breaks, corrosion, or loose connections. Pay close attention to the connections at both ends.
* Check the Instrument Cluster: This is less likely, but a faulty gauge itself is possible. Testing the gauge's resistance might be necessary using a multimeter. Replacing the instrument cluster is a major undertaking and should be a last resort.
3. Replacing the Fuel Gauge (If Necessary):
If after checking the sending unit and wiring, you determine the gauge itself is faulty, you'll need to replace it:
* Access the Instrument Cluster: This usually involves removing the steering wheel, steering column shroud, and potentially the dash bezel to access the instrument cluster. A repair manual is essential here.
* Remove the Instrument Cluster: Carefully disconnect all wiring connectors and remove the cluster.
* Replace the Fuel Gauge: This often requires carefully unscrewing or unclipping the gauge from the cluster. Many instrument clusters have gauges that are soldered in, making replacement more complex.
* Reassemble Everything: Carefully reverse the removal process, ensuring all connections are secure.
Important Considerations:
* Repair Manual: A repair manual specific to your 1998 Chevy Blazer is absolutely essential. It will provide detailed diagrams, torque specifications, and step-by-step instructions.
* Safety: Working with fuel systems requires caution. Always disconnect the negative battery terminal, and work in a well-ventilated area.
* Complexity: Replacing a fuel gauge on a Blazer isn't a beginner-level job. If you're not comfortable working on car electrical systems or aren't mechanically inclined, it's best to take it to a qualified mechanic.
In short: Don't jump to replacing the gauge. Thoroughly diagnose the problem, starting with the most likely culprits (sending unit and wiring). If you are not comfortable performing this type of repair, a professional mechanic should handle this repair.
