What Parts to Replace When the Heater Isn't Hot?

[SanColeman]

When the heater isn't hot, you may need to replace the thermostat. The reasons for the heater not being hot include: insufficient coolant, damaged thermostat, clogged heat exchanger, circuit failure in the heating system, etc. The details are as follows: Insufficient Coolant: Due to damaged components in the engine's water circulation system, leaks at interfaces, or blown cylinder gaskets, the coolant may be insufficient. This results in only a small amount or no coolant circulating in the heater pipes, causing the heater to not produce heat. The solution is to ensure the engine's water circulation system is functioning properly and then replenish the coolant. If there are other issues, repair them first and then add coolant to the normal level. Thermostat Malfunction: If the thermostat was damaged during previous repairs due to issues like high water temperature, it might remain stuck in the open position. This causes the engine's water circulation to stay in a large loop continuously. Combined with low external temperatures and efficient heat dissipation, the engine's water temperature struggles to rise, leading to a lack of heat from the heater. The solution is to install or replace a new thermostat.

[Pauline]

A few days ago, my car's heater was blowing cold air, and it took some effort to fix it. I first checked the coolant level—it was full, but the temperature wouldn't rise. The mechanic said a clogged heater core is a common issue, where hot water can't circulate, resulting in cold air. In the end, replacing the heater core solved the problem. I recommend you check the heater core first—if it's leaking or has too much rust buildup, it needs replacement. A faulty thermostat could also be the culprit; low coolant temperature leads to cold air, and replacing a thermostat isn't expensive. For daily maintenance, always use qualified antifreeze and don’t delay repairs, as it can affect defogging and safety. I personally perform regular system maintenance to prevent issues.

[SanTimothy]

When encountering insufficient heating, you should check several components. The heater core is prone to clogging or leaking, preventing hot water flow and resulting in no heat—replacing it solves the issue. A faulty thermostat can prevent the engine from reaching proper operating temperature; try installing a new one. A stuck heater control valve can also cause problems, and replacing it after inspection is straightforward. My general recommendation is to start with simple diagnostics: drive a few kilometers—if the temperature gauge reads normal, inspect the heater core or valve; if abnormal, replace the thermostat. Don’t overlook coolant quality, as excessive impurities can easily clog components.

[PaisleyLynn]

Focus on replacing the heater core or thermostat. If the radiator is clogged, there's no heat source, so replacing the radiator works quickly. If the thermostat opens late and the water temperature is low, replacing it will solve the problem. Regularly check the coolant level and top it up if it's low. Get it replaced as soon as possible to avoid issues in winter.