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No Heat From The Heater

A heater that blows cold or lukewarm air usually means low coolant, a stuck-open thermostat, air in the cooling system or a blend door fault.

Normal risk

Not a driving risk in itself, but low coolant can lead to overheating. Demisting may also be impaired.

Short answer · Why is my car heater blowing cold air?

The heater uses hot coolant from the engine. If the coolant is low, the thermostat stays open so the engine never warms up, or air is trapped in the system, the heater stays cold. A blend door or control fault can also keep the air cold even when the engine is warm.

On this page

Safe checks you can do

  1. Check the coolant level when coldLow coolant is a common cause.
  2. Watch the temperature gaugeIf it stays low, suspect the thermostat.
  3. Feel both heater hoses when warmIf both are hot, the problem is inside the dashboard.Hoses can be very hot.

Questions that narrow it down

  1. Does the temperature gauge stay low?Thermostat stuck open.
  2. Is the coolant low?Leak.
  3. Is it cold on one side only?Blend door on that side.

Possible causes

Listed without ranking. Use the questions above to see which ones fit your car.

  1. Low coolantNot enough flow.
  2. Thermostat stuck openEngine stays cold.
  3. Air in the cooling systemAfter repairs.
  4. Blocked heater coreDeposits.
  5. Blend door or control faultAir not routed.

Questions about No Heat From The Heater

Is it safe to drive without heat in winter?

Clear windows are a must. If the windscreen does not demist, do not drive.

Does a cold heater mean the engine will overheat?

Not necessarily, but low coolant can lead to it.