Water or Fog Inside Your Side Mirror? A Brisbane Humidity Guide
By Duber, The Car Mirror Man · Car Mirrors Australia · Updated October 2026 · 13 min read
Short answer: a little morning fog on the outside of the glass is normal. Fog, droplets or water on the inside of the mirror is not. It means the cover, the glass edge or the drain gap has let water in. Caught early, the fix is often glass from $135 or a cover from $150 to $300. Left alone, the water can reach the folding motor and the wiring.
In Brisbane? We can replace the glass and renew the fit at your home or work, anywhere across the metro — see our full Brisbane mirror service.
Brisbane is humid for most of the year. The Bureau of Meteorology puts the average 9am relative humidity at 63%, and it climbs to 70% in June [1]. Add about 83 days a year with at least a millimetre of rain [1], and your side mirrors spend a lot of time wet.
Most of the time that is fine. A mirror is built to shed water. But when the glass, the cover or the seals have been knocked, water gets in and stays in. This guide shows how to tell the difference, what usually causes it, and what each fix costs.
The parts, and what each one costs
A side mirror is made of separate parts. Which one broke is what decides the price — not the badge on the car.
Fog outside versus fog inside
There are two very different problems, and people mix them up.
The quick test is simple. Wipe the glass with your hand. If the fog stays, it is on the inside. If you can see droplets, a tide line, or a fine film that looks like steam trapped in a window, it is also on the inside.
Why a sealed-looking mirror lets water in
A side mirror looks like a solid shell. It is not airtight. It has a glass panel clipped onto a backing plate, an outer cover, a mounting base, and usually a small drain gap so that any water that does get in can leave again.
Water follows the same rule everywhere: warm moist air cools and turns back to liquid when it meets a cooler surface [2], and the temperature at which it starts is called the dew point [4]. Inside a mirror housing that happens on the back of the glass and on the inside of the cover. A little of it is normal and the drain gap handles it. The trouble starts when more gets in than can get out.
Cause one: a cracked or chipped cover
A cover that has been knocked in a carpark often has a hairline crack you can barely see. In dry weather it does nothing. In a Brisbane storm it is a funnel.
Rain runs down the door, finds the crack, and drips onto the glass backing plate. If the cover has been scuffed rather than cracked, check the edge where it meets the glass. A gap there does the same job. A cracked cover is a $150 to $300 fix, and it is the lowest-cost way to stop the water.
Cause two: loose glass or a damaged edge seal
The glass is held to its backing plate by clips and an edge fit. A knock can shift it a millimetre. That gap lets in humid air every time the mirror cools overnight.
The tell is fog that shows up on one edge first, or a mirror that has a slight rattle when you tap the housing. Glass-only replacement starts from $135 fitted, and it takes Most jobs take 20 to 40 minutes. It also renews the fit, which is the real fix.
Cause three: a blocked drain gap
Many housings have a small low point where water is meant to leave. Dirt, wax and the odd spider web can close it. Then even normal moisture has nowhere to go.
Cause four: the pressure washer
A pressure washer pointed straight at a mirror base pushes water past seals that were designed for rain, not a jet. Car washes do the same thing at speed.
If the fog started the day after a wash, that is your answer. Keep the spray off the mirror base and the gap under the cover, and let the mirror dry in the sun. If it does not clear in a day or two, something is damaged.
What the water does next
Fog on the glass is the harmless stage. The expensive stages come later, and the order is predictable.
Water sits on the back of the glass. Visibility drops. Nothing is broken yet.
The reflective coating on the glass breaks down where the water sits. You see dark blotches that spread from the edge.
Water reaches the plug that feeds the heater, indicator or folding motor. Green or white crust appears on the pins.
The mirror stops folding, the indicator flickers, or the heating stops. By now a glass-only job has become a motor or a powered unit.
That is why we say fix the cause while the glass is still the only thing affected.
What each fix costs in Brisbane
| What broke | What it costs |
|---|---|
| Mirror glass only | From $135 fitted |
| Cover / housing | $150 to $300 |
| Plain full unit | $200 to $350 |
| Powered unit (fold, adjust, indicator) | $350 to $500 |
| Blind-spot, camera or auto-dim | Quoted per vehicle |
A powered unit carries the folding motor, the adjusters and the indicator. It is $350 to $500, and it is the part water can damage.
Anything with blind-spot monitoring, a camera or auto-dimming glass is quoted per vehicle, because the part moves the price, not the labour.
Heated glass and water
Heated glass has a thin element bonded to the back of the panel. It clears outside fog quickly [5]. It does not fix a mirror that is wet on the inside. If water is trapped behind a heated panel, the element can corrode and the heating stops.
The heater on a heated mirror is usually linked to the rear demister switch. If the rear window demists and the mirror does not, that points to the mirror, not the car.
Can you dry it out and leave it?
Sometimes. If the cover is intact, the glass is tight and the fog came after a wash, parking in the sun for a day or two will often clear it. That is a sound first step.
If it comes back within a week, or you can see a crack, a gap or a rattle, drying is only a delay. The water is getting in from somewhere, and it will get in again.
Does water inside a mirror fail a safety check?
Fog on its own is not the issue. The rear vision mirror has to give a clear view and be free of damage that reduces it, which is the standard the national design rule sets for these mirrors [3]. A mirror so fogged or spotted that you cannot see through it is a view problem.
In Queensland a safety certificate is needed when registration is transferred to a new owner [7]. If you are heading for one, read our guide to safety certificates and side mirrors in Queensland first.
How we fix it at your place
We come to you. Send a photo of the mirror, with a close shot of the fog or droplets if you can. We confirm the part and the price from the photo, before anyone drives out, which is the kind of clear quote the consumer guarantees expect [8].
Straight on, in daylight. Add one of the inside edge of the glass if the water is visible.
Glass, cover, motor or whole unit, with a price.
Home, work or the carpark. Most jobs take 20 to 40 minutes.
Agreed before anyone drives out. Mobile fitting is included, with no separate call-out charge.
A five-minute check you can do at home
You do not need tools to work out which cause you have. Do these in order and you will usually know what to tell us.
Wipe the glass. If the fog stays, it is inside. Note which edge it starts from.
Run a finger around the cover. Look for a hairline crack, a chip, or a gap where it meets the glass.
Press the glass edge gently and tap the housing. A rattle or movement means the glass or cover is loose.
Fold and adjust the mirror. Slow, noisy or stuck movement means water may have reached the motor.
Take a photo of what you find. That photo is the quickest route to a fixed price.
When Brisbane mirrors fog most
Relative humidity compares how much moisture is in the air with the most it could hold at that temperature [6]. For Brisbane, the Bureau of Meteorology figures show 9am humidity is highest in the cooler months, around 70% in June [1].
That is why morning fog on a mirror is more common in winter, and why it fades as the day warms up. Fog that is still there at lunchtime, on a dry day, is the one to look at.
Summer works differently. Heat and sudden storms push water at the mirror from outside. A cracked cover that stayed quiet for months can suddenly leak after one heavy afternoon storm.
Why a small crack is worth fixing early
Small cracks feel harmless. They do not look like damage. But a mirror cover is a roof for what sits underneath it, and a roof with a crack in it leaks.
| Stage | What you see | What it usually costs |
|---|---|---|
| Early | A hairline crack, no fog yet | Cover, $150 to $300 |
| Middle | Fog or droplets inside the glass | Glass from $135, plus the cover if cracked |
| Late | Mirror will not fold or the indicator flickers | Powered unit, $350 to $500 |
The middle and late stages cost more because the water has had time to reach the parts that cost more. The early fix is the lowest-cost one by a wide margin.
What Brisbane drivers tell us
A mirror that is looked at early is usually a short job.
Every review quoted on this site is a real, verified customer review. We do not write them and we do not edit them.
Keeping Brisbane humidity out for good
A few small habits help. They will not fix damage, but they stop small problems growing.
Every band above comes from our national price guide, which is the single source of truth for what we charge. If you want the full breakdown by part and by vehicle, read our side mirror replacement cost guide.
We come to you in five cities
Every job is mobile. We drive to your home, your work or the car park the car is sitting in, and the mirror is fitted where the car is.
Frequently asked questions
Why is there water inside my side mirror?
Water has got past the cover, the glass edge or the seals, or the drain gap is blocked. In Brisbane's humid air that trapped moisture turns into fog and droplets on the back of the glass.
Is fog on the outside of my mirror a problem?
No. Outside fog on a humid morning is normal and wipes off. Fog that stays after you wipe is on the inside.
Will water inside the mirror damage it?
It can. The reflective coating can spot, and the water can corrode the connector that runs the folding motor, heater or indicator. That is why early fixes cost less.
Can I just let it dry out?
If the mirror is intact and the fog followed a wash, a day or two in the sun often clears it. If it returns, the water is still getting in.
How much does it cost to fix?
Glass from $135 fitted, a cover $150 to $300, a powered unit $350 to $500. Blind-spot, camera or auto-dim mirrors are quoted per vehicle.
Should I drill a hole or use silicone?
No. Both make it worse. A hole lets more water in and silicone blocks the gap water uses to leave.
Do you come to me in Brisbane?
Yes. We fit mirrors at your home, work or wherever the car is parked, across the Brisbane metro.
Can you tell what is wrong from a photo?
Usually yes. A clear photo of the mirror, plus a close one of the fogged edge, is enough to name the part and give a fixed price.
More on Brisbane mirrors
Based in Brisbane? These cover the rest of it.
Sources
- Climate statistics for Brisbane, Bureau of Meteorology — 9am relative humidity by month and days of rain of 1 mm or more — www.bom.gov.au/climate/averages/tables/cw_040913.shtml
- Condensation, Wikipedia — why moisture forms when warm humid air meets a cooler surface — en.wikipedia.org/wiki/Condensation
- Australian Design Rule 14/02 — Rear Vision Mirrors, Federal Register of Legislation — www.legislation.gov.au/F2006L02663/latest/text
- Dew point, Wikipedia — the temperature at which air can no longer hold its moisture — en.wikipedia.org/wiki/Dew_point
- Defogger, Wikipedia — how heated mirror and window elements clear fog — en.wikipedia.org/wiki/Defogger
- Humidity, Wikipedia — what relative humidity measures — en.wikipedia.org/wiki/Humidity
- Safety certificates, Queensland Government — when one is required — www.qld.gov.au/transport/registration/roadworthy
- Consumer guarantees for services, Queensland Government — delivered with due care and skill, within a reasonable time — www.qld.gov.au/community/fair-trading/consumer-rights-complaints-and-sca
Prices and information in this article are indicative only and reflect real quoted jobs at the time of publication. Costs vary with vehicle, part availability and features. Send a photo for an exact fixed price.
