1. Coolant Level and Condition:
* Check coolant level: Open the radiator cap (carefully, when cool!) and check the coolant level. Low coolant prevents heat transfer. Top it off with the correct 50/50 mix of coolant and distilled water if needed. (Never use just water.)
* Inspect coolant condition: Is the coolant clean and green/orange (depending on the type used), or is it rusty, brown, or sludgy? A severely contaminated system indicates potential internal damage.
2. Thermostat:
* Verify thermostat function: A stuck-closed thermostat prevents coolant from circulating to the heater core. You'll need to locate the thermostat (usually near the engine's top hose) and check if it opens when the engine reaches operating temperature. You might need a thermometer to confirm temperature. A faulty thermostat is a common culprit.
3. Heater Core:
* Check heater core hoses: Locate the two hoses connected to the heater core (usually under the dash). When the engine is warm, feel these hoses. They should both be hot. If one is cold and the other hot, the heater core might be clogged or leaking internally. If both are cold, the problem is likely upstream (thermostat, coolant level).
* Heater core blockage/leak: A clogged heater core restricts coolant flow. A leak won't necessarily prevent *some* heat, but would result in weak or inconsistent heat and potentially a sweet smell (from leaking coolant). This often requires replacement.
4. Blend Door Actuator:
* Check blend door operation: The blend door controls the flow of air between hot and cold. A malfunctioning blend door actuator (a small motor) might be stuck on cold air, even if the coolant is circulating. This usually requires diagnosis to see if the blend door is stuck and whether it's the actuator, linkage, or the blend door itself at fault.
5. Water Pump:
* Check water pump operation: While less likely if you have heat elsewhere (like the radiator), a failing water pump won't circulate coolant properly, affecting heat to the heater core. Look for leaks around the pump and listen for unusual noises.
6. Head Gasket (Less Likely, but Serious):
* Exhaust gas in coolant: A blown head gasket can allow exhaust gases into the coolant, reducing pressure and efficiency. Look for excessive pressure in the coolant system, milky oil (oil and coolant mixed), or white smoke from the exhaust. This is a major engine repair.
Troubleshooting Steps:
1. Start with the easiest checks: coolant level and condition.
2. Next, move to the thermostat. A faulty thermostat is a very common cause of this issue.
3. Check the heater core hoses – temperature difference between them is a strong indicator.
4. If all else fails, consider the blend door actuator and water pump as possibilities.
5. A blown head gasket is the least likely, but most serious possibility.
Important Notes:
* Safety First: Always let the engine cool completely before working on the cooling system to avoid burns.
* Consult a Repair Manual: A repair manual specific to your 1991 Chrysler LeBaron will be invaluable in providing detailed diagrams and procedures. You can find these online or at auto parts stores.
* Professional Help: If you're not comfortable working on your car's cooling system, take it to a qualified mechanic. Incorrect repairs can lead to serious engine damage.
By systematically checking these components, you'll likely pinpoint the cause of your lack of heat. Remember to replace parts with the correct specifications for your vehicle.
