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uk Transport & mobility emergencies

What to do if…
your vehicle’s heater, defroster, or climate controls fail and visibility is worsening

Produced and maintained by PanicStation.org Published: Last reviewed: Editorial policy UK guide

Short answer

Do not continue once you cannot see enough of the road to drive safely. Slow down smoothly, try the normal demisting controls without becoming distracted, and stop at the first place of relative safety.

Do not do these things

  • Do not continue through a small or shrinking clear patch in the windscreen.
  • Do not lean forward or wipe the windscreen by hand while the vehicle is moving.
  • Do not brake or steer abruptly unless an immediate hazard requires it.
  • Do not handle a phone while driving.
  • Do not stop abruptly in a live traffic lane when a safer stopping place remains reachable.
  • Do not attempt repairs beside moving traffic.
  • Do not use front or rear fog lights unless visibility is seriously reduced, and switch them off when visibility improves.

What to do now

  1. Ease off the accelerator, check your mirrors and increase the distance from the vehicle ahead. Drive only at a speed that allows you to stop within the distance you can see clearly.

  2. Use the windscreen wipers if rain, spray or snow is affecting the outside of the glass. Switch on your headlights when visibility is seriously reduced and use dipped headlights in fog.

  3. If you can operate the controls without losing concentration, select airflow towards the windscreen, increase the fan and choose a warm temperature. Turn on the air conditioning, heated windscreen and rear-window demister if fitted, and select fresh outside air rather than recirculation.

  4. Open a side window slightly if it is safe and practical. This may reduce moisture inside the vehicle while you move towards somewhere safe to stop.

  5. If the glass is not clearing promptly, signal early and stop at the first suitable place away from moving traffic, such as a lay-by, car park, service area or side road. If you cannot reach one because visibility has become too poor, stop as safely as you can and switch on the hazard warning lights.

  6. Once fully stopped, use a clean, dry cloth to clear condensation from the inside of the windscreen and front side windows. Do not resume the journey unless you have a clear view and the glass will remain clear.

  7. Contact a breakdown provider or arrange recovery if the controls remain faulty or visibility starts worsening again. You do not need to identify or repair the fault at the roadside.

  8. On a motorway, leave at the next junction or enter a service area if you can do so safely. Otherwise, move left into an emergency area or onto the hard shoulder where one is available, stop and switch on the hazard warning lights.

  9. If you stop in an emergency area or on the hard shoulder and can leave safely, exit through a door on the side away from traffic and wait behind a safety barrier where possible. Keep well away from the carriageway and contact your breakdown provider.

  10. If the vehicle stops in a live motorway lane, or it is not safe to get out, stay inside with your seat belt fastened and hazard warning lights on. Call 999 and ask for the police, or use the vehicle’s SOS function if available.

What can wait

You do not need to diagnose the fault, choose a repairer, order parts or decide how to complete the journey now. Those decisions can wait until everyone is away from moving traffic and the vehicle is in a safe location.

Important reassurance

Stopping because you cannot maintain a clear view is a proportionate safety decision. Delaying or abandoning the journey is safer than continuing when you cannot see properly.

Scope note

This guide covers the first actions needed to protect visibility and reach a safer pause. Fault-finding, repairs and decisions about onward travel may require a breakdown service or qualified vehicle technician.

Important note

This is general road-safety information, not mechanical, legal or other professional advice. Follow instructions from the police, road operators and emergency services, and call 999 where there is immediate danger.

Additional Resources

Closely connected guides that may be useful during the same situation or its immediate aftermath.

About this guide

This guide was produced and is maintained by PanicStation.org using its published editorial process. Official and specialist sources are checked where relevant, and AI-assisted tools may be used for drafting, organisation, and consistency checks. The site operator remains responsible for publication, revision, and removal decisions.

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