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Discussion Starter #1
I've noticed that my Exterior Temp Readout is slow to change first thing in the morning. Even coming out of the garage (where it's about 50) into a 75-degree day, the temp readout moves very slowly up to the much warmer outside temperature...sometimes taking as long as 15 minutes to read correctly.
Once it gets to the proper outside temp, it seems to have no problem registering changes at a normal rate.
Does my X need a cup of coffee first thing in the AM? Anyone else noticed this? It's not exactly a big problem, but when everything else on the car is pretty much perfect, you start to notice the little things.
 

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Leader....
My MDX exterior temp display works pretty much the same as yours... I have not tried giving the 'X' coffee. Maybe that would work... Compared to some of my other vehicles, I do find it is a little slower coming up to the nearly correct temp. I think it is a matter of the area around the temp sensor warming up or cooling down to match the outside temp.
 

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Discussion Starter #3
I've thought the exact same thing. I'd bet the actual "sensor" is not isolated from the bracket holding it...thus, the bracket's slow rise to current temp delays the sensor's ability to move up. Not a brilliant design.
 

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The ability of the sensor to display the outside temp is NOT the primary reason they put the sensor in....

It's purpose is to tell the PCM the temp of the air entering the intake. The computer then knows the density, and can inject the right amount of fuel.

If the air is cool (and it will be if it is being drawn in through the cool radiator, cool engine interior, cool airbox, it will appear to be 'sluggish'. It will take some time for all the materials in the air path to warm up.

And really, the thing they want is not the outside air temp, but the actual air temp entering the intake.


i don't know enough about the design to render an opinion on it's brilliance...

Ard
 

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Discussion Starter #5
Ard,
If the exterior temp sensor's primary purpose is "to tell the PCM the temp of the air entering the intake," then its very slow rise to actual outside temperature is not just inaccurate, it may not be good for engine efficiency.
In the scenario where you leave a cold garage first thing in the morning and drive out into a 75-degree day, my sensor takes about 15-20 minutes to move up to the actual outside temp. So, presumably, it's telling my engine that the outside air it's gulping is a lot colder than it really is.
I don't know enough about the design to really comment on its brilliance, either...but, an asset of digital thermometers is their ability to register temperature changes almost instantly. Apparently mine doesn't do that. I'll ask my dealer at first service.
 

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Simple to check:

Take a digital thermometer, place the thermocouple next to the sensor in the vehicle, see if there is a major difference.

You won't get a dealer to do this (it's not in the book), but thats the way to see if it is indeed a latency in the system or the sensor, or a real offset between the billboard at the bank versus the air being drawn through the radiator directly at the sensor...

If I remember this weekend, I'll try it.

Ard
 

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According to the '01 Electrical Troubleshooting manual, the outside air temp sensor is for the heater/AC only, and is mounted immediately behind the center of the front bumper. It has a gray plug with two wires, brn/wht and yel/grn. It is not connected to any other air-temp sensor circuits.

Mine was stuck at 32 degrees the other day for about half-an-hour after I ran it through the carwash on a very cold day; maybe it was coated with ice?
 

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Discussion Starter #8
Yeah, frostyra, I've noticed that a trip to the car wash will paralyze the temp readout for at least a half-hour. The temperature probe must be situated in a spot that retains a little bit of water (or, in your case, ice).
 

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frostyra-

You are correct- there is another sensor in the intake manifold for engine air-(Intake Air Temperature Sensor) and no connection between the climate control and PCM (there is a digital buss that I thought was the link, but it is for the display)

Now that I a looking at the manual (always a danger to post first, read later) it appears the sensor allows the Climate Control to sensor the temp near the AC coils.

Still worth trying to measure the latency. Perhaps it has to do with the position of the sensor around the fluid filled radiator and coils?

Ard
 
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