You are here: Forums Sedans Chevrolet Cobalt Outside thermometer reading stuck

Outside thermometer reading stuck

2 messages,  Last post on Jul 12, 2009 at 6:13 AM

You are in the Chevrolet Cobalt Forum. Your Hosts are pat & karens

What is this discussion about? Chevrolet Cobalt, Coupe, Sedan

Messages Page 1 of 1 All Messages Displayed

Go To Msg # Search This Discussion

#1 of 2 Outside thermometer reading stuck by tcalof Jul 04, 2009 (8:04 pm)
The outside temp readout on my '08 Cobalt LT is stuck on 19C. It's been sitting on 19C for the past week despite being outside in the sun in 25C temps and in the garage at 15C temps. All other functions of the DIC work properly. Any way to reset the thing or check the sensor for a loose wire? Where is the sensor? Any help appreciated. Replies to this message: tcalof (Jul 12, 2009 6:13 am)
#2 of 2 Re: Outside thermometer reading stuck [tcalof] by tcalof Jul 12, 2009 (6:13 am)
Replying to: tcalof (Jul 04, 2009 8:04 pm) Problem explained. There was nothing wrong with the sensor. The algorithm for displaying outside temperatures is bizarre. Here's the quote:   GM part # 25775833   Ambient Air Temperature Sensor The ambient air temperature sensor is a 2-wire negative temperature co-efficient thermistor. A 5-volt reference and signal circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor operates within a temperature range of -40°C to +60°C (-40°F to +140°F). The HVAC control module receives a class2 message from the instrument panel cluster (IPC). The ambient air temperature sensor is mounted in the forward engine area, behind the left front headlamp. This causes an air flow issue due to the sensor's location and can effect the ambient air update display parameter in the DIC of the vehicle. For model year 2008 the ambient air temperature sensor will have a new location closer to the grill airflow. In the present position, it is exposed to limited airflow from the grill before it reaches the radiator. The sensor signal varies between 0-5volts. The HVAC control module converts the signal to a working temperature range. The ambient air temperature sensor algorithm uses 3 pieces of information, outside air temperature data, vehicle speed, and time the engine was turned off. The ambient air temperature is updated and displayed by the DIC under the following conditions:   Conditions DIC Display   If the current ambient air temperature value is cooler than or equal to the old temperature value, displays outside actual temperature. Display updates every second.   Vehicle speed is in excess of 33 mph.   If the current ambient air temperature value is warmer than the old temperature value, displays last temperature recorded. Vehicle speed is less than or drops below 18 mph during last ignition cycle. No update.   New ambient temperature exceeds the previous ignition cycle recorded ambient temperature, and vehicle speed exceeds 18 mph but is less than 33 mph, displays outside actual temperature. Display will be updated at a slow rate.   Vehicle speed is greater than or equal to 45 mph (for at least 3minutes), displays outside actual temperature Display updates at a quicker rate.

Messages Page 1 of 1 All Messages Displayed

Go To Msg # Search This Discussion

You are here: Forums Sedans Chevrolet Cobalt Outside thermometer reading stuck