Heater/AC problem
03-03-2007, 05:15 PM
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Heater/AC problem
Hi. I have a 2001 SSEi and been having a problem with the automatic heater/AC for some time. When it was under warranty, I told the dealership that it would often start blowing cool air after I've been driving for a long time (hour or more), and it kind of does the opposite when using the A/C. Even with both controls set at same temp. Of course they never found it to be a problem. Anyway, for a while now the external temp display will keep climbing, sometimes in to the 90s, and then go back to where it started. It varies a lot. Lately, when I change it from defrost to any other mode, it starts blowing cooler air. Have to turn it back on defrost to stay warmer. Doesn't have much air flow out the floor either. I love the car but have never liked the way this heater/AC works. Now it'* bad enough that I'm going to have to take it in, but thougt I'd see if any of you have any idea what I can check for first. I've search this great site but have not found any thing on this. Thanks in advance. Lots of great info on here.
-Bob
-Bob
03-03-2007, 05:31 PM
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There have been some problems with the air mix actuators, but that doesn't sound like your problem. Does the temperature vary in accordance with the outside temperature reading? If I had to guess, I'd start with the temperature sensor that'* in front of the radiator. Take a resistance reading of it, then warm or cool it, and see if it varies smoothly. If the resistance varies immediately (without any warming or cooling), that sensor would be the problem. If not, then it is likely the timing circuitry within the control unit.
Edit - Sorry....welcome to the club!
Edit - Sorry....welcome to the club!
03-03-2007, 05:43 PM
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Thanks for the reply. I assume the outside temp affects it some. However, don't believe the ext temp is ever right. Yesterday the ext temp said it was about 45, although it was around 32 outside, and then climbs up into the 60s then starts over. It is just silly how this thing is working. Had wondered where the ext temp sensor was for it. I'll have to check that. Was wondering if there was any way to "reset" this control. Thought about pulling the fuse for it for a few minutes and see if it changed anything. If any other ideas, appreciate the input.
Bob
Bob
03-05-2007, 12:40 PM
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Your problem may be electronic, but before you go too far, you can make some free checks on the mechanical parts of the system. First, check the coolant level in the radiator when the car is cold. Low coolant will starve the heater core and make it heat and cool sporadically. If the coolant is low, look for and find the leak. If you cannot find an external coolant leak and are still losing coolant, that is a whole 'nother problem. If coolant is OK, with car at normal operating temperature feel the feed and return hoses to the heater core. They should both be hot. (Be careful of moving belts and pulleys!) The return may be a little cooler if the heater core is heating the cabin air in the car. Anyway, these are free checks you can perform to rule out those possible causes for your problem.
03-05-2007, 07:25 PM
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Thanks for the info Bill. The coolant level is fine and has not been a problem. The heater does put out hot air, especially on defrost. Still today, same problems. Defrost works fine but when putting it on top and floor, there is some cool air on the floor. The top air is warm. And cool air if I turn it on dash vents. It just changes after running for a while. I can also drive 14 miles to work with the defrost on and the blower stays on high with the auto setting. When I change the mode to top and floor, the blower drops way down and not much coming out either place. I've even had a problem a few times where I couldn't get much of any defrost out the top even with the blower on high. All the windows would fog up while driving and had to wipe the inside of the windshied. After turning it off for a while, it would work again. Couldn't get it to do this at the dealer. Don't see it having anything to do with the coolant or the thermastat. Have had similar problems with the AC in the summer too. Seems like it has to be an electronic problem. Was hoping someone else had this type of problem and got it resolved, or how to reset this silly thing. Did I mention how much I hate this heater/AC?? 
--Bob
--Bob
03-05-2007, 07:28 PM
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To me, one of the flaws in the GM automatic temperature control system is that when you are in heating mode and the interior temperature begins to climb to the point where it has to go into bi-level mode to bring the temperature back down, it doesn't temper the air that it is bringing in from the outside. This will often result in 60 degree or even cooler air coming out the vents. It is only really noticable when the outside temperature is in the 55-65 degree range. I had a SHO with automatic controls and it did temper the incoming air so there was a much better comfort factor in those conditions.
03-05-2007, 09:24 PM
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Originally Posted by IndyBob
Thanks for the reply. I assume the outside temp affects it some. However, don't believe the ext temp is ever right. Yesterday the ext temp said it was about 45, although it was around 32 outside, and then climbs up into the 60s then starts over. It is just silly how this thing is working. Had wondered where the ext temp sensor was for it. I'll have to check that. Was wondering if there was any way to "reset" this control. Thought about pulling the fuse for it for a few minutes and see if it changed anything. If any other ideas, appreciate the input.
Bob
Bob
03-06-2007, 12:13 AM
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True Car Nut
As Imidazol mentioned, sometimes just removing, cleaning, and putting some dielectric grease on the connections solves the problem. Give that a try first. This is a description of its operation.
Ambient Outside Air Temperature Sensor Description
This sensor is located in front of the radiator. The ambient temperature sensor is a temperature-sensitive resistor whose resistance varies inversely with temperature. As air temperature increases, resistance decreases. As air temperature decreases, resistance increases. The Instrument Panel Integration Module (IPM) monitors the ambient temperature signal and uses this information to display outside temperature on the driver information center and helps determine command signals.
During periods of city traffic and idle conditions engine heat can surround the area of the ambient temperature sensor and cause temperature readings that are higher than the actual ambient air temperature. To help eliminate these false readings programming techniques are used to minimize unwanted temperature variations.
A temperature memory feature is used in the IPM ambient temperature programming to help provide greater accuracy under engine restart conditions. If engine coolant temperature is less than 10°C (50°F) above the ambient temperature sensor reading, or a two-hour ignition off timer has expired then the actual sensed ambient temperature is displayed. However, if engine coolant is greater than 10°C (50°F) above the sensor reading, memorized ambient temperature is displayed. This is the displayed temperature sensed when the engine was previously operating. At vehicle speeds greater than 32 kmH (20 mph) the ambient temperature display may be allowed to increase, but only after a built-in 80-second time delay which allows for ambient air to cool the sensor. The 80-second time delay starts when vehicle speed reaches or maintains at least 32 kmH (20 mph) . If the sensor reading is ever less than the displayed value or if the vehicle speed is 72 kmH (45 mph) or greater there is no delay and ambient temperature changes are displayed as rapidly as possible.
The scan tool is able to provide an instance temperature update.
This sensor is located in front of the radiator. The ambient temperature sensor is a temperature-sensitive resistor whose resistance varies inversely with temperature. As air temperature increases, resistance decreases. As air temperature decreases, resistance increases. The Instrument Panel Integration Module (IPM) monitors the ambient temperature signal and uses this information to display outside temperature on the driver information center and helps determine command signals.
During periods of city traffic and idle conditions engine heat can surround the area of the ambient temperature sensor and cause temperature readings that are higher than the actual ambient air temperature. To help eliminate these false readings programming techniques are used to minimize unwanted temperature variations.
A temperature memory feature is used in the IPM ambient temperature programming to help provide greater accuracy under engine restart conditions. If engine coolant temperature is less than 10°C (50°F) above the ambient temperature sensor reading, or a two-hour ignition off timer has expired then the actual sensed ambient temperature is displayed. However, if engine coolant is greater than 10°C (50°F) above the sensor reading, memorized ambient temperature is displayed. This is the displayed temperature sensed when the engine was previously operating. At vehicle speeds greater than 32 kmH (20 mph) the ambient temperature display may be allowed to increase, but only after a built-in 80-second time delay which allows for ambient air to cool the sensor. The 80-second time delay starts when vehicle speed reaches or maintains at least 32 kmH (20 mph) . If the sensor reading is ever less than the displayed value or if the vehicle speed is 72 kmH (45 mph) or greater there is no delay and ambient temperature changes are displayed as rapidly as possible.
The scan tool is able to provide an instance temperature update.