Outside temperature off
09-04-2009 | 10:12 AM
#1
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Joined: Jul 2008
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From: NYC
Outside temperature off
I have an '08 G coupe 6spd and just noticed the other day that the outside temperature gauge is off by about 10 degrees. In the past it has always been pretty accurate. does anyone else have this problem, and do you know if the sensor is mounted in a bad spot?
09-04-2009 | 11:06 AM
#2
When I purchased mine I was told that temp is for the climate control system and it may not read the correct temp. I have noticed that the temp is really off when the car is not moving. Don't quote me but I think the positioning of the sensor is the reason for this. The M has two sensors, one for the climate system and one for the outside temp.
09-04-2009 | 12:49 PM
#3
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Joined: Apr 2009
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From: Southern NH
^ not sure what you mean by that. Whoever told you that does not understand the purpose of that sensor and the overall HVAC system.
The external temp sensor is mounted in front of the radiator on the lower middle area. It's a thermistor whose resistance value changes with temperature which then varies the voltage seen by the system processor. It's used by the HVAC system to control the internal temp along with several other sensors (internal ambient temp, inside intake air temp, sunload, and even the engine coolant temp, refrigerant pressure and vehicle speed).
Related to the HVAC system:
The unified meter and A/C amp. includes a processing circuit for the ambient sensor input. However, when the temperature detected by the ambient sensor increases quickly, the processing circuit retards the unified meter and A/C amp. function. It only allows the unified meter and A/C amp. to recognize an ambient temperature increase of 0.33
Related to the temp display on the instrument panel:
I've had a lot of experience with this type of sensor in my prior car where it was common for it to fail or the connector would get corroded and affect the resistance of the circuit.
The external temp sensor is mounted in front of the radiator on the lower middle area. It's a thermistor whose resistance value changes with temperature which then varies the voltage seen by the system processor. It's used by the HVAC system to control the internal temp along with several other sensors (internal ambient temp, inside intake air temp, sunload, and even the engine coolant temp, refrigerant pressure and vehicle speed).
Related to the HVAC system:
AMBIENT TEMPERATURE INPUT PROCESS
The unified meter and A/C amp. includes a processing circuit for the ambient sensor input. However, when the temperature detected by the ambient sensor increases quickly, the processing circuit retards the unified meter and A/C amp. function. It only allows the unified meter and A/C amp. to recognize an ambient temperature increase of 0.33
°C (0.6°F) per 100 seconds.
As an example, consider stopping for a few minutes after high speed driving. Although the actual ambient temperature has not changed, the temperature detected by the ambient sensor will increase. This is because the heat from the engine compartment can radiate to the front bumper area, location of the ambient sensor.
OUTSIDE TEMP
Control outline
If the conditions above are met and you still see a significant error in the temperature reading then the most likely reason is the temp sensor may be failing either due to water/corrosion or it's defective. The dealer will be able to test it against the temp/resistance specs. • - The unified meter and A/C amp. receives the ambient sensor signal from the ambient sensor.
• - The unified meter and A/C amp. calculates the ambient temperature according to the ambient sensor signal, and transmits it to the combination meter.
• - The indicated temperature is corrected by the ignition switch signal, the ambient sensor detection temperature, and the vehicle speed signal. It does not increase if the vehicle speed is less than 20 km/h (12 MPH).
Correction process (Ignition switch OFF → ON)
The ambient temperature sensor detection temperature is not displayed in real time if all of the following conditions are fulfilled.
The indicated temperature before the ignition switch OFF is displayed.
• The ignition switch OFF time is less than 3.5 hours
• The ambient temperature sensor detection temperature is higher than the indicated temperature before the ignition switch OFF
Correction process (Ignition switch ON)
Perform the following correction if the ambient sensor detection temperature is higher than the indicated temperature when the vehicle speed is 20 km/h (12 MPH) or more.
• Shorten the update time of the indicated temperature according to the increase of the vehicle speed.
• Increase the indicated temperature by 1°C per 1 minute until it reaches to the ambient temperature detection value when the ambient sensor detection temperature is higher than the indicated temperature at 8°C or more.
NOTE:
The ambient sensor input value that is displayed on DATA MONITOR of CONSULT-III is the value before the correction. It may not match the indicated temperature on the information display.
• - The unified meter and A/C amp. calculates the ambient temperature according to the ambient sensor signal, and transmits it to the combination meter.
• - The indicated temperature is corrected by the ignition switch signal, the ambient sensor detection temperature, and the vehicle speed signal. It does not increase if the vehicle speed is less than 20 km/h (12 MPH).
Correction process (Ignition switch OFF → ON)
The ambient temperature sensor detection temperature is not displayed in real time if all of the following conditions are fulfilled.
The indicated temperature before the ignition switch OFF is displayed.
• The ignition switch OFF time is less than 3.5 hours
• The ambient temperature sensor detection temperature is higher than the indicated temperature before the ignition switch OFF
Correction process (Ignition switch ON)
Perform the following correction if the ambient sensor detection temperature is higher than the indicated temperature when the vehicle speed is 20 km/h (12 MPH) or more.
• Shorten the update time of the indicated temperature according to the increase of the vehicle speed.
• Increase the indicated temperature by 1°C per 1 minute until it reaches to the ambient temperature detection value when the ambient sensor detection temperature is higher than the indicated temperature at 8°C or more.
NOTE:
The ambient sensor input value that is displayed on DATA MONITOR of CONSULT-III is the value before the correction. It may not match the indicated temperature on the information display.
I've had a lot of experience with this type of sensor in my prior car where it was common for it to fail or the connector would get corroded and affect the resistance of the circuit.
09-04-2009 | 08:10 PM
#4
I've noticed that mine reads wrong at least for the first few seconds (maybe minutes) then it updates. The car must be moving.
Example:
Car is parked on the 4th level of our garage. Cranked it this morning and the temp guage read 77. By the time I went down 4 levels and hit the street it changed to 71.
Example:
Car is parked on the 4th level of our garage. Cranked it this morning and the temp guage read 77. By the time I went down 4 levels and hit the street it changed to 71.
02-19-2016 | 05:45 PM
#5
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Joined: Feb 2016
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Have had a rapid warmup the last couple of days here in West Texas; into the upper 80's. The sensor reads pretty much a constant 55 degrees but increases about 3-4 degrees while the car is moving around town. Would driving the car at highway speeds "shake" the sensor into reading 86 degrees and not 58??
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05-28-2016 | 04:03 PM
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05-28-2016 | 04:05 PM
#14
Last edited by bigc; 05-28-2016 at 04:10 PM.
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05-28-2016 | 04:49 PM
#15
LOL, understood. I lived in Naples for 15 years, bout 3 hours South of you, before moving here two years ago. It's hotter here in Texas during the summer but far, far less humid. It's actually more tolerable. I really don't miss Southwest Florida summers.