If you’ve jumped in the car on a chilly Hamilton morning and fired up the heater, only to watch your windscreen stubbornly stay foggy, you’re not alone. Happens all the time – especially for folks running around town, popping up Ulster Street, hitting Te Rapa Road traffic, or dodging potholes around Nawton. It’s not just annoying. It’s actually risky driving with a fogged-up windscreen, especially in the crazy wet winters we get here and the stop-start stuff through Chartwell lights.

How come there’s condensation on my windscreen?

Let’s break it down. When the outside’s cold (pretty standard from Tamahere to Rototuna come winter), and you hop into your nice toasty car, your breath and body add heaps of moisture to the air inside. That warm, damp air hits your freezing windscreen and, boom, fog central. Pretty common if you usually park outside, like half of Hamilton does, or especially if you’ve got a bit of water leakage going on somewhere in the cabin.

Getting rid of that fog – Practical tips

The usual fix is just cranking your heater, aiming the hot air right at the glass, and letting it do its thing. It should clear up fairly quick. If it doesn’t, there’s probably something wrong with the heating or the vents. Time for a mechanic to have a squiz.

If the heater’s sort of working but not brilliant, here’s what we normally suggest in the workshop, whether you’re driving an old Nissan Serena or a newer Skoda Fabia:

  • Point your vents up at the windscreen and side windows. Full blast on the fan helps heaps.
  • Don’t blast the hottest air right away. Start milder and wind the heat up after a minute or two.
  • Throw on the aircon, even if it’s cold out. It dries the air faster – we see this work even on those random Daihatsu Boon imports rolling in from Morrinsville.
  • Set your system for fresh air, not recirculate – dragging in dry outside air helps clear glass quicker.

Why won’t my heater clear condensation?

If you’re still battling fog after all that, your heating system might be on the blink. Common stuff we see come through from Raglan, Cambridge, or even the shopping centre at The Base are:

  • Low coolant or bad antifreeze in the radiator – might be from a slow leak, cracked hose, whatever. If the coolant level drops, the heater stops doing its job.
  • Thermostat playing up, so the hot coolant never actually gets to where it should.
  • Blower fan is toast, or barely spinning – pretty common on older Suzuki Swifts and the odd Mercedes B-Class from town.
  • Heater core blocked with gunk, so you barely get any hot air inside. Not fun if your car’s just blowing cold up Dinsdale hill.

Best get it checked, just to be sure. We’ve seen people try to drive into winter without heat, and you end up with more fog and sometimes engine overheating too. No point adding to your woes.

Other reasons heaters in NZ cars don’t do their job

  • HVAC issues: If your heating, ventilation, and air con system (HVAC) is stuffed, you won’t get decent airflow or dehumidification. That’s a real pain after school drop-off on wet mornings.
  • Blocked drain in HVAC: Sometimes gunge gets in the drain, builds up under the dash, and you get a wet carpet smell – pretty common with Honda Freed and Toyota Alphard models.
  • Dead blower motor: If the air isn’t moving much, you get patchy defogging, which doesn’t cut it on a frosty morning out at Whatawhata.
  • Heater core leak: You’ll get that sweet coolant smell in the cabin, and fog just gets worse. Seen this a bunch on VW Golfs lately, but it can happen on anything.
  • Dirty cabin filter: Blocks air, slows everything down. Loads of import vehicles haven’t had theirs changed since coming off the boat.

Should I get my car heater sorted?

Honestly, yeah. It’s too dangerous to drive around Frankton with a foggy windscreen hoping you can keep wiping by hand. Plus, these issues don’t fix themselves. They get worse, cost more down the line, and can even fail your WOF during inspection. If you need help with your car heater, or you want to make sure you’re all set for another gnarly Waikato winter, give us a shout. Grimmer Motors has sorted out everything from Mazda Demios to Fiat Puntos. We’ll check what’s going on and give you proper options – not just patch-ups.

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