If your defroster or defogger is not working, it can make it difficult to see clearly through your windscreen and windows, especially in cold or wet weather. Since visibility is essential for safe driving, this issue should be inspected and repaired as soon as possible.

What does it mean if the defroster or defogger isn’t working?

The defroster clears condensation or frost from the windscreen and rear window by blowing warm air or using electric heating elements. If it’s not working, the airflow, heating, or electrical system may have a fault preventing proper operation.

Common causes of defroster or defogger failure

• Blower motor not working or weak airflow
• Faulty heater core or low coolant preventing warm air flow
• Clogged or broken air vents or ducts
• Blown fuse or wiring fault in the rear window defogger
• Damaged rear window heating elements
• Faulty switch, relay, or control module

Why do you need to fix this problem quickly?

Without a functioning defroster or defogger, your visibility can be severely reduced, especially in bad weather. This is a safety hazard and can also cause your car to fail a Warrant of Fitness (WOF) inspection.

How do you know when to get it checked?

You should book an inspection if:

• The windscreen fogs up and won’t clear with the defroster
• The rear window heating grid does not warm up
• Airflow from vents is weak or cold even when heater is on
• Electrical warning lights appear related to the HVAC system
• You notice leaks or a sweet smell (possible heater core issue)

What happens during an assessment?

A mechanic will:

1. Check blower motor and airflow operation
2. Inspect heater core and coolant level
3. Test rear defogger switch, fuse, and wiring
4. Examine rear window heating elements for breaks
5. Check HVAC controls and relays
6. Advise on repairs or part replacement as needed

How much does it cost to fix?

Minor fixes such as replacing a fuse or switch may cost $100–$250. Heater core repairs range from $600–$1,200+. Rear defogger repairs may cost $200–$500 depending on whether wiring or the glass heating elements are faulty.

Is it unsafe to drive with a broken defroster or defogger?

Yes. Reduced visibility from fogged or frosted windows is a serious safety hazard and can make your car illegal to drive in poor conditions. The issue should be repaired before driving in cold or wet weather.