Fickle temp gauge in 2008 accord?

Hello,

Today I noticed that for a few hours my temp gauge in my accord decided to
stay at 59F even though the temp outside had moved from 59F to 70F. Later,
in about 3 hours the temp gauge reads the right temp of 87F. Other weather
conditions are clouds and fog that later changed to sun, but I never heard
of this happening? Any thoughts on this? Car was moving during the time that
temp read out was stagnant.

Thanks,
Al

 

The thermometer in my 07 Accord EX-L reads right except in the summer when
it reads 6-8 degrees higher than the actual temp...

 

Okay, well mine seems to be the right temp when its reading it. Although
sometimes there is a long delay in when it switches to the actual temp.
Sometimes it take 30 min or so. I didnt notice this in the winter so i am
thinking it has this happen more often in the winter.

 

From the March '07 issue of Honda Service News, put out by Honda for its
dealerships techs:


<begin quotation>

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 skew the indication.

<end quotation>


Clear as mud?

 

iow, alfred, the great worrier, never drives more than 19mph!

 

Thanks Tegger, that was some good information. I'll keep that in mind.
So what that seems to tell me also is that if you're driving the car
in the summer, theres a good chance that the temp will be inacurate
since the coolant is going to be pretty warm. That would explain why
it started going haywire this weekend when we got that heat wave.

Actually, I change a tire going faster than 19 mph. I'm a speed demon
at times, so no you're wrong there Jim! I don't worry, I'm detail
oriented and analyze everything I come across.

Al

 

Honda uses a weird software algorithm for their outside temperature
gauge which is based on the reading when you start up, how long you have
been driving and on ours at least it will not change more than one
degree per minute even if the conditions are right. In the summer in
stop and go driving the net results is that it is almost never even
close to right.

Our Accord is an '03 and perhaps they have yet to make the algorithm
smarter.

 

Yes, and it is still a dumb algorithm. The net results is that in
summer stop and go city driving the gauge is almost never right. It
also works badly in extreme mountain driving such as crossing the Sierra
Nevadas in the winter, where the outside temperature can in fact vary
much more than one degree per minute of driving.

 

And people wonder why folks get nervous about the Maintenance Minder!