1. The Obvious:
* Coolant Level: Check the coolant level in the radiator and overflow tank. Low coolant means the system can't transfer heat effectively. Top it off with the correct 50/50 mix of coolant and distilled water if needed. *Never* open a hot radiator or pressure vessel.
* Thermostat: A stuck-closed thermostat prevents coolant from circulating to the heater core. This is a very common cause. A stuck-open thermostat will allow the engine to run cold, but still provide heat (although potentially less efficiently).
* Heater Control Valve: This valve controls the flow of coolant to the heater core. If it's stuck closed, no coolant reaches the core. This can be electrically or vacuum controlled, depending on your model. Check for vacuum leaks if it's a vacuum-operated valve. Listen for the valve clicking when you change the temperature setting.
* Blend Door Actuator: This controls the mix of hot and cold air. A faulty actuator might prevent hot air from reaching the vents even if the heater core is working. This is usually inside the dashboard, and diagnosing this usually requires some disassembly.
* Worn out blower motor: If the fan doesn't work or runs weak, you won't get any air, regardless of heat. Check the blower motor fuse and relay.
2. Less Obvious:
* Heater Core: A clogged or leaking heater core prevents hot coolant from transferring heat to the air. A leak can lead to coolant in the cabin.
* Water Pump: A faulty water pump won't circulate coolant properly, affecting both engine temperature and heater function. Listen for unusual noises from the water pump.
* Air in the System: Air pockets in the cooling system can prevent proper circulation. Bleeding the cooling system may be necessary.
* Radiator Fan: While less directly related to heat, a malfunctioning radiator fan can lead to overheating, preventing enough heat from being available for the heater core.
* Wiring and Fuses: Check all fuses and wiring related to the heater system, including the blower motor, heater control valve, and any related components. Look for corrosion, broken wires, or loose connections.
Troubleshooting Steps:
1. Start with the easy checks: Coolant level, thermostat (feel the upper radiator hose to see if it gets hot), and heater control valve (listen for its operation).
2. Check the blower motor and fuses: Ensure the fan is working correctly.
3. If coolant is low, address the leak: A leaking heater core is a common culprit.
4. If all else fails, consult a repair manual or a mechanic: A 1990 Camaro is a bit older, and a repair manual will provide specifics on your vehicle's cooling system. A mechanic can perform a more thorough diagnosis.
Remember safety first! Work on a cool engine and always wear appropriate safety gear. Coolant is toxic.
