2004 to 2020 Mazda 3 Forum and Mazdaspeed 3 Forums banner

1 - 18 of 18 Posts

·
Registered
Joined
·
87 Posts
Discussion Starter #1
My Mazda 3 has a tendency to steam up on cold days. The result is that when its very cold, you get ice form on the inside of the windscreen.
Got in the car yesterday, there was ice on the inside of the windscreen (and outside), but the external temperature gauge said 1 deg C. Now, the law of physics says that can't be true. My conclusion, the temperature gauge reads too high. So, beware when you hit the road and it says (say) 1 deg C as t may still be below zero.

UK based.
 

·
Working Class Hero
Joined
·
3,610 Posts
If the car was sitting for a while, the temp gauge won't read accurately. It takes some time and movement to get things right.

Sent from a Samsung that doesn't explode.
 

·
Registered
Joined
·
155 Posts
from what i've read the sensor picks up heat from the road as well, hence the higher reading. And then there is the case of ambient heat generated by the engine, I am sure no matter how insulated it does affect it a little.
 

·
Registered
Joined
·
73 Posts
The ambient temp gauge in my '13 Fiesta was always spot on, however the Mazda's always seems to read 1-2 degrees C more than what the weather service reckons.
 

·
Registered
Joined
·
327 Posts
Plus there's retained heat / cold in the materials in the car. If the air temp just happened to raise enough to 1 degree above freezing it doesn't mean that the glass has, and when it does that it will instantly melt. Due to the variables as listed above the temp gauge in your car is a ballpark at best.

If ice on the road is what you're concerned about you should be paying extra caution any time the temp gauge is reading in the 3-4 degree temp range or lower and the roads look wet as cold soaked asphalt can cause icy conditions despite a positive air temperature.
 

·
Registered
Joined
·
6 Posts
Noticed the same - the external temp sensor seems to be reading 2-3 degrees more than expected.
You can come up with a miltitude of explnations why it behaves like this, but the fact is - most other cars get it right, even having the sensor mounted in rougly the same spot behind the grille.
A Honda Accord I owned a while ago would even let you adjust the delta for +-3 degrees if you found the sensor to be misreading, would be great if Mazda allowed this as well.
 

·
Registered
Joined
·
124 Posts
If the car was sitting for a while, the temp gauge won't read accurately. It takes some time and movement to get things right.

Sent from a Samsung that doesn't explode.
mine's read +5F higher than actual when starting up in the morning.

after 5min driving, it still reads +2F higher than actual.
its close enough for me but still annoying thats its not 100% accurate in this day and age.

(actual = what the external thermometer at my house says.)
 

·
Working Class Hero
Joined
·
3,610 Posts
Mine generally matches what my phone says after a few minutes of driving.

Sent from a Samsung that doesn't explode.
 

·
Registered
Joined
·
8 Posts
Note that water does not always freeze only when ambient temperature is at or below 0°C. There are other factors, such as some evaporation can cause the leftover fluid to depress to below ambient and freeze. With some wind, this can make water freeze without ambient temperature reaching 0°C, so using frozen water in the environment is not a precise nor accurate indicator for whether ambient temperature is at or below 0°C.
 

·
Gearhead
Joined
·
1,841 Posts
Do not specifically know about Mazda 3, but most outside temperature sensors are located within the engine compartment, and once the motor is warmed up and radiating heat, the external temp gauges consequently read a degree or two warmer than real. And most have an initial time delay, i.e., even though my garage may be 50 degrees, takes about a half mile before it gets close to reading the real outside temp.

As the Owner Manual notes regarding the Outside Temperature Gauge:

"Under the following conditions, the outside temperature display may differ from the actual outside temperature depending on the surroundings and vehicle conditions:
Significantly cold or hot temperatures.
Sudden changes in outside temperature.
The vehicle is parked.
The vehicle is driven at low speeds."
 

·
Registered
Joined
·
56 Posts
do gen 3's have a numerical temp gauge?? I thought the 2015's dont
 

·
Registered
Joined
·
673 Posts
Where is the temperature sensor? I expect it will be an electronic (thermistor?) sensor and should be accurate. Most cars need to be driven a few miles to get an accurate reading of the ambient air flow, else the sensor is just measuring the temperature of static air close to the sensor. This static air may have been heated by convection/radiation from the car body or engine components which may be hotter than ambient temperature.
 
  • Like
Reactions: GerryB

·
Registered
Joined
·
15 Posts
I too have '15 Touring. Always +2~3 F more than the actual temp. This is after driving for a while. While my wife's Rogue shows accurate temperature. (We usually compare the data with our phone or sign boards on the road that show the temperature). No idea why Mazda is not spendin some money on this.
 

·
Registered
Joined
·
673 Posts
I too have '15 Touring. Always +2~3 F more than the actual temp. This is after driving for a while. While my wife's Rogue shows accurate temperature. (We usually compare the data with our phone or sign boards on the road that show the temperature). No idea why Mazda is not spendin some money on this.
How do you know which is giving the most accurate temperature reading. You would need need to check with reference to a correctly calibrated thermometer.
 

·
Registered
Joined
·
6 Posts
Well if you see like 5 displays and the thermometer at home and your other car and they all show roughly the same +-0.5 degree of each other, and Mazda says it's +2-3 degrees more, the conclusions are rather obvious.

The sensor itself is located behind the front grill towards the driver side, you can see it through the grill. On most cars it's located in the same area so they all should be heavily affected by residual heat, but somehow they don't. That's valid after a few minutes of driving of course.
 

·
Registered
Joined
·
6 Posts
By the way, here's Mazda's take on this.
In theory if you replug the sensor, you should see the real temperature it measures before any adjustments assumed by the car. The problem is - you either have to have extremely small hands of remove the front bumper to get to it.

I can't post URLs, but the link is to this forum, so just please add mazda3revolution.com in front :)

/forums/attachment.php?attachmentid=149610&d=1456886461
 

·
Registered
Joined
·
93 Posts
No it is not. As this is something that I have done or my job (properly siting meteorological instruments) for many years I can tell you that roadside thermometers are the absolute worst when it comes to accuracy. Bank thermometers and personal backyard thermometers are never located property especially with regards to sun exposure. They are notoriously poor. And because their siting is so poor they rarely agree with 0.5 degrees F. Plus the accuracy is questionable as well. That is true for the Mazda thermometers too of course. But if either are withing 3 degrees that is good considering neither are tested or calibrated over time.
 
1 - 18 of 18 Posts
Top