Outside temperature accuracy

Well, how to check the outside temp?

 

Temp at home by a thermometer will be different than a thermometer at the airport that they use to tell you over the radio or report on weather sites. They may be the same, but there is always a difference. Temperature is very local.

The Prius as most cars have the sensor somewhat influenced by heat, but there really isn't a way around that. 1C to 2C accuracy is normal for standard temperature sensors, so if you have 10 thermometers all exactly the same side by side, there is a chance one will be -2C/-4F different then the other which could be +2C/+4F different. So if the temperature was really 75F, you could see anything between 71F and 79F. Usually these are calibrated to within +/-0.5C but that is still +/- 1F difference plus some additional error from location + the actual temperature variance where you are versus where you are getting the other reading from + the accuracy of that other reading.

2F lower is usually the actual difference on Toyota/Lexus vehicles after they are warmed up. When cold, the variance will be greater and usually read low, not high.

 

I meant how you check the temp from the car.

The only screen to see the temp is "Drive Information". I think I've read somewhere here while in the other screen when driving: "Energy Monitor", "Eco Score", ... I can glance to see the temp outside by tapping some button but I don't remember. I couldn't find the thread either and already tried a lot of way with no available.

 

Just touch (no need to press) the recirculate/fresh air button on the steering wheel controls.

 

Keep in mind if you park your car in the garage and then go driving it will take a few short minutes for that temperature gauge to get to the correct outside temperature. I found that out the other day while driving as it has been rather cool here in WI lately.

 

+1 on having to keep moving to keep fresh air flowing across the outside temp sensor in order to get an accurate reading. That said, I have yet to find a reason to doubt the thermometer; it seems to coincide with NWS data and it's always different than the bank signage thermometer, which we all know are always wrong, LOL.

Just to throw it out there; how do you know your home thermometer is accurate? It's also possible your cars' thermometer is simply outside the tolerance curve. If you honestly consider the temp reading to be a problem, bring it to the dealer and see if they'll replace it under warranty.

 

I did notice it was reading higher, I was going to look where they had located it. I would assume its dow in the grill area, but I had not noticed it when I had peered under there.

 

I have found mine to be reasonably accurate assuming that the car hasn't been sitting in the sun for any length of time.

 

I know my home thermometer is off above about 90F and below about 40F. But between those numbers my car outside temp usually agrees with the home numbers. Out of those ranges I trust the car temp more than the home temp.

 

Put your car in the garage and let it cool off. If you have a reasonably accurate thermometer, check the indoor garage temperature, preferably in the early morning, and then check to see what the car sensor is reporting. Should be pretty close. You can do the same thing outside before the sun gets on the car or ground around the car. Most thermometers take about 10 minutes or more to stabilize, so make sure you leave the thermometer where it will be used for a while. The longer the better. You could also find someone with another c and leave them next to each other a while and see if they register the same temperature.

National Weather Service thermometer standard is +/- 2 degrees F, so some small deviation should be expected.

 

I have about five time/temp sites to check against the car on my way to work. All but one are more than a mile away from home.

The car is usually within a degree or two from the time/temp, and a good deal of the time is spot on. The variance between the roadway and the obelisk can be several degrees so I don't worry much about it.

If you want real worry, my car clock is almost 45 seconds off. That is really bugging me...

 

Okay, an interesting experience today. I park underground so it is a reasonably stable environment. When I got in the car, it read 25°C and I would say this is probably about right.

As I drove the 15 minute drive to work, the outside temperature reading very slowly climbed to 28°C.

The actual outside temperature at the time was 40°C.

 

If our OAT gauge is the same as Gen3, then I think it fit what the Gen3 Repair Manual describes:

If you let it sit for longer time, it may climb to 40°C.

Vincent

 

Okay, I just checked on the car which is under the office. It now reads 36°C, so this seems consistent with your suggestion. Official weather stations in the vicinity report 39.0 to 40.4°C.

 

Mine went from 41° in the garage to 3° once I was outside and started driving, within about 8 minutes.

Droid RAZR HD MAXX

 

For the trip home it was 38°C when I hopped into the car, edging up to 39°C after about five minutes outside.

When I entered an underground shopping centre car park, the temperature displayed dropped rapidly. It was 36 when I got out of the car and down to 32°C when I got back in. It stayed at that level for the five minute drive home.

It seems to be much happier going down than up!

 

There will most certainly be variances however I have found that my temp read-outs we're within reason and credible. I have not noticed any large deviations between current temps on the radio or my home digital outside thermometer. (unlike my Smart Car)