1. Check the Obvious:
* Temperature Control Settings: Make absolutely sure the temperature is set to "HOT" and the fan is on a sufficient speed. Seems obvious, but it's the first thing to check!
* Airflow Direction: Ensure the air vents are directed toward you and not set to defrost or floor only.
* Coolant Level: Check your coolant (antifreeze) level in the radiator overflow tank. Low coolant means the system can't circulate enough heat. If low, add coolant of the correct type (check your owner's manual). *Never open a hot radiator!*
* Thermostat: A malfunctioning thermostat can prevent the engine from reaching the proper operating temperature, thus reducing or eliminating heat. A stuck-closed thermostat is a common culprit.
* Radiator Fan: Check if the radiator fan is working. If not, the engine might overheat, preventing the coolant from reaching the heater core.
2. More Advanced Troubleshooting:
* Heater Core: This is a small radiator located inside the vehicle that warms the air. A clogged or leaking heater core is a common cause of no heat. A leak would result in coolant leaking into the passenger compartment (you'd likely smell it). A clogged one just won't transfer heat effectively. Replacing a heater core is a moderately involved job.
* Heater Core Hoses: Check the two hoses connected to the heater core. Both should be warm when the engine is at operating temperature. If one is cold, there's a blockage or problem with coolant flow to the heater core.
* Water Pump: A faulty water pump prevents coolant circulation throughout the engine, including the heater core. A failing pump can make a whining noise.
* Blend Door Actuator: This motor controls the blend of hot and cold air. A malfunctioning actuator might be stuck in the cold air position. This is often diagnosed with a scan tool to check for error codes.
* Vacuum Lines: Some heater controls rely on vacuum lines. A leak in these lines can prevent proper operation of the blend door.
* Circulation Pump (Optional): Some models (though less likely in 1998) have a secondary electric pump for the heater. If equipped, this could be faulty.
3. Diagnosis and Repair:
* Visual Inspection: Look for obvious leaks, loose hoses, or anything out of the ordinary under the hood and inside the vehicle around the heater controls.
* Scan Tool: A scan tool can read diagnostic trouble codes (DTCs) that might point to a specific problem with the climate control system. Auto parts stores often offer free code reading services.
* Professional Mechanic: If you're not comfortable with car repair, it's best to take your Cutlass to a qualified mechanic for diagnosis and repair. Heater core replacement, for example, can be a messy and time-consuming job.
Important Safety Note: Working on a car's cooling system involves hot coolant and potential for burns. Allow the engine to cool completely before attempting any repairs. Use appropriate safety gear (gloves, eye protection).
