Car symptom
Heater not blowing hot
No heat can be as simple as a clogged cabin filter, or as serious as a head gasket. Narrow it down by temperature and airflow.
Most likely causes
- Thermostat stuck open
- Air lock / low coolant
- Blocked heater core
- Blend door actuator
- Clogged cabin filter
Checks to run
- Check the temperature gauge
- Verify coolant level and bleed the system
- Feel both heater hoses
- Inspect the cabin filter
Tools you may need
Cooling pressure tester
Confirm before replacing. These are hypotheses to check — never buy parts on a guess. If the fault involves brakes, airbags or fuel under pressure, use a professional.
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FAQ
It depends on the cause. Some causes are cheap and quick; others (like a head gasket or seized caliper) need attention soon. Work through the checks in order and confirm before replacing parts.
Start with the free checks listed here. If they involve high voltage, fuel under pressure, airbags or brakes, let a professional handle it.
The interactive diagnostic asks targeted questions to narrow it down, and every cause must be confirmed with a measurement — never guess.