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Thread: Outside temp sensor - what does it do anyway?

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    Charter Patron D'Ecosse's Avatar
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    Outside temp sensor - what does it do anyway?

    What function does the outside air temperature sensor (located in front bumper) actually do anyway?
    I haven't had one in there since I've owned the car & it doesn't seem to affect anything.
    I would think that it shouldn't have any effect on the control of the inside temperature (system should look to the inside sensor & tell controller how to react).
    I'm wondering however if maybe it has some effect on the condensor fans? i.e perhaps they only come on when there is a certain temperature differential?
    Anyone know what the mode is for the condensor fans to run?
    Maybe I need to just break down & buy the sensor, but I'd like to understand the function & contribution.
    93 Red/Black NSX

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    Registered User j14nsx's Avatar
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    I thought its for the air con.

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    Registered Vendor Briank's Avatar
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    That sensor goes directly to the climate control. Using that information it can adjust how it operates. Like when you need to cool the car because the sun is out but the air temp. is low, cool fresh air could be brought in instead of running the AC. Without it you may be running the AC more.

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    Charter Patron D'Ecosse's Avatar
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    Originally posted by j14nsx
    I thought its for the air con.
    Originally posted by Briank
    That sensor goes directly to the climate control.
    C'mon guys, I know that ......
    (I have degree in electronic eng. incidentally)

    Using that information it can adjust how it operates. Like when you need to cool the car because the sun is out but the air temp. is low, cool fresh air could be brought in instead of running the AC. Without it you may be running the AC more.
    I think it either operates in recirc mode of fresh air mode, depending on what mode you select; does it really switch between these modes when in Automatic?; similarly I'm not really convinced the sunlight sensor does a whole lot either. But the designers must have had some use or they wouldn't be there.
    It's frustrating because there is no real information about how the system responds to the inut sensors - it's just a "black box" controller. Even a state table of "if sensor A < sensor B, Z happens" would be helpful in the description of operation. I think we all know fundamentally the object is to control the inside temp, so the primary sensor for controlling that has to be the inside temp sensor.
    Now if someone had a schematic ......
    Inquiring minds want to know
    93 Red/Black NSX

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    Registered Vendor Briank's Avatar
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    The climate control will switch to recirculate in auto I have seen it just crank the temp control to the coldest setting. Yes there is very little info on the operation of the climate control unit so a lot of stuff is just supposition. I guess you could just take a hair dryer to the sensor and or freeze spray and see what happens.
    Or in your case connect a variable resistor (pot) and see how the unit reacts. Looking at the service manual a 12K pot would be a good choice 12K = 35F and 1K = 104F

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    Charter Patron D'Ecosse's Avatar
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    Originally posted by Briank
    ...Or in your case connect a variable resistor (pot) and see how the unit reacts. Looking at the service manual a 12K pot would be a good choice 12K = 35F and 1K = 104F
    There's a good idea - see what actually happens as the "temperature" changes.
    93 Red/Black NSX

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    Charter Platinum THonda's Avatar
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    D'Ecosse, since you are the Man! how's about trying to figure out a way to use that outside temp sensor to actually give a reading somehow inside the car. I don't know why i like the outside temp reading so much, but it's the one thing I will miss off the M3.

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    Charter Patron D'Ecosse's Avatar
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    Originally posted by THonda
    ... how's about trying to figure out a way to use that outside temp sensor to actually give a reading somehow inside the car. ....
    I know, isn't that something? It was one of the things I looked & looked for, how to read the outside temp & when I found it didn't appear possible, I pretty much gave up on the idea of installing it back again!
    93 Red/Black NSX

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    Registered Vendor Briank's Avatar
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    Any thing can be done with enough time and money . It is likely you could tap into the voltage across the sensor (thermistor) and feed it to a display device. Some thing as simple as a DVM would work but you would need chart to convert volts to degrees. Or you could use an off the shelf voltage display the problem is always zero and span adjustments.

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