Problem w/ambient temperature sensor
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3rd Gear
Joined: Aug 2006
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Problem w/ambient temperature sensor
I have a problem with my 2000 corvette. The outside air temperture is way off and is causing airconditioning and heater problems because the car thinks it's below freezing outside. I have already replaced the ambient temperature sensor which is located next to the radiator. This did not fix my problem. Has anyone else had this problem?
Drifting
Joined: May 2000
Posts: 1,917
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From: Southern NH
Originally Posted by torchred2kvette
I have a problem with my 2000 corvette. The outside air temperture is way off and is causing airconditioning and heater problems because the car thinks it's below freezing outside. I have already replaced the ambient temperature sensor which is located next to the radiator. This did not fix my problem. Has anyone else had this problem?
If replacing the sensor did not fix the problem, then the issue is likely with the connector wiring having corrosion. The temp reading will decrease as the impedance of the sensor increases, so it's likely that the connector is not making a clean connection.
If you disconnect the sensor and leave the circuit open, the HVAC unit will default to 68*F so you can use the AC. If it doesn't read 68*F, then the circuit is not completely open. Try cleaning the connector (WD-40 will do a good job), or worse case cut it off until you can get a replacement connector.
Remeber that the temp display will not change immediately if the car was started less than 3 hours ago - you'll need to drive it above 25 MPH for 90 seconds before it will update.
Advanced
Joined: Jun 2005
Posts: 53
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From: Bellevue WA
Make sure you are replacing the correct air temp sensor. The one outside passenger compartment is not "ambient air" it is "outside air temperature sensor. I think you will find that there is a different sensor inside the passenger compartment that measures the inside temp and it is the one that determines whether to heat or cool the interior based upon your air conditioning setting. Don't think the outside temp has much bearing on the problem. After all, logically you want to know when the inside of the car is at the desired temp, regardless of outside air temp.
Le Mans Master
Joined: Dec 2001
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From: Winchester TN
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Originally Posted by YLWFVR
Make sure you are replacing the correct air temp sensor. The one outside passenger compartment is not "ambient air" it is "outside air temperature sensor. I think you will find that there is a different sensor inside the passenger compartment that measures the inside temp and it is the one that determines whether to heat or cool the interior based upon your air conditioning setting. Don't think the outside temp has much bearing on the problem. After all, logically you want to know when the inside of the car is at the desired temp, regardless of outside air temp.
The outside air plays a big role in how much heating or cooling the hvac must do to the air to adjust the temp to meet the needs of the cabin occupants.
If it is 90 outside, and the hvac is set to 72, the ac must work harder to cool the air to the specifed temps, just as if it is 45 outside the car, the hvac will heat the incoming air -
The hvac system is very elaborate and sophisticated - not a simple thermostatic control.
It even uses a light sensor to determine if it is a sunny out or if the sun is blocked, or if it is night - all impact the hvacs operation.
best regards -
mqqn
Drifting
Joined: May 2000
Posts: 1,917
Likes: 3
From: Southern NH
Originally Posted by mqqn
Hi YLWFVR -
The outside air plays a big role in how much heating or cooling the hvac must do to the air to adjust the temp to meet the needs of the cabin occupants.
If it is 90 outside, and the hvac is set to 72, the ac must work harder to cool the air to the specifed temps, just as if it is 45 outside the car, the hvac will heat the incoming air -
The hvac system is very elaborate and sophisticated - not a simple thermostatic control.
It even uses a light sensor to determine if it is a sunny out or if the sun is blocked, or if it is night - all impact the hvacs operation.
best regards -
mqqn
The outside air plays a big role in how much heating or cooling the hvac must do to the air to adjust the temp to meet the needs of the cabin occupants.
If it is 90 outside, and the hvac is set to 72, the ac must work harder to cool the air to the specifed temps, just as if it is 45 outside the car, the hvac will heat the incoming air -
The hvac system is very elaborate and sophisticated - not a simple thermostatic control.
It even uses a light sensor to determine if it is a sunny out or if the sun is blocked, or if it is night - all impact the hvacs operation.
best regards -
mqqn
Plus a real BIG reason the outside air temp sensor is important in the use of the HVAC. If the outside temp reading is below ~38*F, it prevents the AC from coming. Hence, as the original poster indicated, with an erroneous low reading he can't turn the AC on.
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Instructor
Joined: Apr 2006
Posts: 161
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From: Cypress TX
just in case you want to check your temp sensor, per my 98 service manual the resistance in the temp sensor is as follows..try checking it in the ambient temp then in ice water. mine was giving me erroneous ohm readings, so to make sure that it wasn't a combination of sensor/wiring or ac head controller, i put a 6,800 (if i remember correctly) ohm resister in the connector and it reads a steady 94 degrees F.. sensor is the only problem...
32 F = 32,654 ohm
50 F = 19,903 ohm
68 F = 12,493 ohm
86 F = 8,056 ohm
104 F = 5,327 ohm
32 F = 32,654 ohm
50 F = 19,903 ohm
68 F = 12,493 ohm
86 F = 8,056 ohm
104 F = 5,327 ohm
Drifting
Joined: May 2000
Posts: 1,917
Likes: 3
From: Southern NH
Originally Posted by torchred2kvette
The problem was fixed by putting conductive grease in the connector. It was a corosion problem which is strange since this car never goes out in the rain! Thanks for all of the replies.
Great.It seems that most electrical problems in this car is due to a connector issue (the weakest link). I found one connector where the pin was not properly crimping the wire so it was making intermittent contact. It's usually the cheapest and easiest place to start.
