Anyone get slow or inaccurate temperature reading for the outside temperature?

Lately it seems the temperature is slow to adjust up. It is nice it doesn't get affected by sunlight and idling, but it has been 7-10 degrees off at times.

how accurate should it be and how long to get there?

 

There is a section in the manual about the temp readings. Basically, the temp reading is effected by the speed and temp at the time you shut your car off and then again as you drive off the next time. It does take time to get a more or less accurate reading. Since the sensor is located in the front bumper it is effected by the pavement, idling, etc. Acura notes that the temp sensor is not a highly accurate instrument and that the info it provides is only a guide as to the temp outside. Should you find the temp readings are high or low when compared to readings from outdoor displays, radio and/or TV info, or you home thermometer, you can adjust the temp on the display plus or minus 3 degrees. Again, all of the info is in the manual.

 

When I first bought the car, I adjusted the temperature to the current outside temperature near the ground at my home. As Rex says above, the instructions are in the manual. It takes several minutes at a speed above 19 mph for the temperature to adjust appropriately. I find the temperature measurement reasonably accurate.

Someone did an excellent writeup on the thermometer for the 3G TL, which is similar to ours. I'll try to find it later and post the link.

 

It's probably worthwhile to say here that the temperature at street level isn't usually going to correspond to the temperature you hear on the radio.

The reason is that the official weather service temperature is measured inside a shaded box mounted 50 feet off the ground. Air is pulled through the box by a fan so the actual AIR temperature is measured.

Down where we humans live, though, the temperature is affected by the sun shining on us, by heat reflected up from the pavement, by heat held by metal car parts, and even by engine heat thrown off by cars and trucks around us. As a result, the temp shown by your car's thermometer will often be higher than the one announced by the weather man.

That's okay by me, since I personally think the temperature I FEEL is more meaningful than the temperature up there in that little wooden box on a pole at the airport. The point, though, is that your car isn't wrong just because it reads a couple degrees higher than the "official" temperature.

And as already pointed out, it will take a little while for the car thermometer to adjust to the real temperature after sitting for awhile. If it's taking more than 6 or 8 minutes of driving to settle down, though, you might want to have it checked.

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The sensor (like the 2nd and 3rd gen TLs) is mounted behind the bumper (behind the license plate holder. As mentioned by others, it is affected by the heat of the radiator when warm, but it's reasonably accurate once underway and it's not affected by sunlight.

 

I have seen this problem with our RL. It does seem to be intermittent.

 

I second what Mike said.

 

Why don't they mount the temperature sensor in the intake so that the measurement will come from airflow (like Mike_TX little box with the fan)? This would measure the air temperature.

Granted, when you re-start a warm-engined car, the temp will be high because of the retained heat, but once the air is flowing through the intake, it should be a fairly accurate air-temp measurement, wouldn't you think?

 

Here is the algorithm used for the outside temp indicator. From the March 07 Acura Service News

"Outside Temperature Indicator Logic Explained

The A/C, the solar blocking glass, and the heater do
such a good job keeping the temperature of the
passenger’s compartment at a comfortable level that
it’s easy to lose track of just how hot or cold it really is
outside. An outside temperature indicator in the
gauge assembly gives you a reality check. But keep
in mind, this indicator isn’t a laboratory-grade
thermometer, and it might not show the same
temperature as you’d see on signs or buildings with
outside temp displays.

The outside air temperature sensor is mounted
behind the middle of the front bumper. The gauge
control module uses measurements from that sensor
to display the outside air temperature.

Because of where the sensor is mounted, it may be
affected by heat coming off the road, the engine, the
radiator, or even the exhaust pipes from other
vehicles. To minimize bogus readings, the gauge
control module follows a certain logic. Here’s how
that logic works:

When you turn the ignition switch to ON (II). . .

• If the engine coolant temperature is 139°F or
lower, the indicator shows the current outside air
temperature.

• If the engine coolant temperature is 140°F or
higher, the indicator shows the temperature that
was stored in memory when you turned the
ignition switch to LOCK (0), no matter what the
sensor behind the bumper currently measures.

The indicator doesn’t refresh until certain criteria are
met:

• If the measured outside air temperature is more
than the indicated temperature, the indicated
temperature rises 1°F every minute once the
vehicle reaches and maintains a speed of 19
mph or faster for at least 30 seconds. As long
as the vehicle speed doesn’t drop below that, the
indicator refreshes every 60 seconds until the
two temperatures match. If the vehicle speed
drops below 19 mph, the indicator doesn’t start to
refresh again until the vehicle speed climbs to 19
mph or faster for more than
90 seconds.

• If the measured outside air temperature is less
than the indicated temperature, the indicated
temperature drops 1°F every 2 seconds until
the two temperatures match, no matter what the
vehicle speed is.

So here’s the bottom line: The outside temperature
indicator seldom delivers readings in real time
because of the many heat sources that could throw
off that indication."