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05 STS
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Discussion Starter · #1 ·
Just curious about something..... not a big issue or problem at all. I have had a number or GM cars with climate control over the years. For most it was a set it and forget it deal. On my 00 and 05 STS on long trips I find I need to keeping bumping up the temperature as the heater keeps getting cooler the longer I drive.

I keep the temperatire on 73 and after say a 3 hour trip in the winter I am up to 84 to stay comfortable. Once you stop like for gas and restart the car you need to run it back to 73.

The external temperature sensor which I know feeds the system the ambient temperature reads true. No problem with the A/C only a winter deal.

Just curious........ I thought this a one off in the 00 model but does the same for the 05???
 

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2006 STS 1SG & 2007 STS 1SE
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14 Posts
I had this problem on my trusty 1993 Buick Roadmaster. I bought it new and within a year I realized that a long drive turned cold. That dealer's service department always claimed 'unable to duplicate'. I persisted.

Finally, two jobs and 300 miles relocated, I took my purportedly out of warranty Buick to my new local dealer. These guys looked at my paperwork and said, 'You reported this issue under warranty, it's covered. We may have to stand on our head to get it fixed." But they did it.

GM's Climate Control often draws air from the cabin (usually near the middle of the dash) down a long tube to a sensor in the depths behind the dash. On a long drive, the cabin gets cooler and cooler and colder and colder when that sensor goes bad or is not installed correctly (that's my bet.) I think the sensor is too close to components that heat up on a longer drive.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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In the 2005+ (didn't check earlier years), the inside temperature sensor is behind the instrument cluster trim at the very end of the aspirator tube. These ones aren't located deep in the dash.

The automatic climate control in these cars use information from an ambient and inside air temperature sensor. The system also adjusts temperature based on the sunload sensor. This is part of the ambient light sensor on the dash. The sunload sensor is split into left and right sides. It's purpose is to determine how much sun is shining on the vehicle and from roughly what side. Temperature in the cabin will decrease (for the driver, passenger or both) when there is more sunlight and increase in the same manner when there is less.

Needless to say, there are several factors that may be contributing to this condition.
 

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2006 Cadillac STS V8 RWD
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50 Posts
Does anybody have a picture of these sun load sensors? I thought the Climate Control uses the middle sensor (the same for external light) to determine if there is sun or not!
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Does anybody have a picture of these sun load sensors? I thought the Climate Control uses the middle sensor (the same for external light) to determine if there is sun or not!
The sunload sensor is all part of that same assembly (small dome shaped sensor near the defrost vent).
 

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Discussion Starter · #6 ·
WOW!!!!!! I'll date myself here but my parents had a Buick Electra 225......which I eventually inherited. That system was all ran by vacumn. It had a lever that we set at an indicated 70 degrees. We had that car 19 years and I don't think we ever moved the lever control in all those years. Cool in the summer warm in the winter.

Somehow this has gotten too complicated!!!!
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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WOW!!!!!! I'll date myself here but my parents had a Buick Electra 225......which I eventually inherited. That system was all ran by vacumn. It had a lever that we set at an indicated 70 degrees. We had that car 19 years and I don't think we ever moved the lever control in all those years. Cool in the summer warm in the winter.

Somehow this has gotten too complicated!!!!
And this is somewhat simplified... If you look at the 2000-05 Bonneville w/Auto Dual-Zone climate control, they use the ambient and inside air temp sensors, a sunload sensor and several additional temperature sensors in the instrument and kick panel duct work.
 
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