Ac issues problem my ambient air temperature sensor ?

2008 PONTIAC GRAND PRIX
180,000 MILES • 5.3L • AUTOMATIC
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LAVELL11
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Hello i send a video my compressor working and air blowing cold. But here's the problem my ambient air temperature sensor was reading the outside air fine but once I starter driving its drop below 16 degrees and compressor shuts off and now the sensor going up and down and not consistent anymore. So I went to oreillys pick up a Dorman and install drive my car to read to the temp and still it remains the same reading its ice on dash but in illinois is 88 degrees plus I had a P0645 code so I have new relay on deck swap it out and still the dash reads ice and compressor not moving. No fuses blown or wire damage. Something is playing with my ambient air temperature sensor I hook up a scan tool my inside temperature under my driver wheel reads accurate but that ambient sensor was at 32 degrees when its hot over here. I don't understand but did this means my compressor clutch going bad because it want turn on when the ambient sensor reading 32 degrees. I dont get it. But when I drive the ambient air sensor bounce around when its new from the store I change so my ambient air sensor its killing me over here. Thinking compressor giving me signs cuz the wires all fine
Jul 14, 2026 at 3:04 AM
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STRAILER
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Yep, this happens when the HVAC control module goes out or the AC clutch coil is shorting out and back feeding the circuit, I would unplug the compressor to see if the sensor reading smooths out and becomes more normal, if so you know the clutch coil is bad. That is what the P0645 code might be telling you. Please let me know what happens.
Jul 14, 2026 at 2:11 PM
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LAVELL11
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Ok i will try that and let you know wssp because this weird never had this problem till now. https://quickshare.samsungcloud.com/52Gs5uFYs5mG hopefully yall can see that I record this morning on my way to work
Jul 14, 2026 at 4:37 PM
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STRAILER
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Can you just upload the video in your response?
Jul 14, 2026 at 6:52 PM
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LAVELL11
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This morning drive. Its definitely this compress my drive home after work read 100 degrees on dash then went straight to 32 degrees compressor is off. Changing soon can yall send me a diagram to change out thanks
Jul 14, 2026 at 7:35 PM
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STRAILER
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Yep, thank for the video. So can I ask if there was any difference when you changed the ambient temperature sensor out? Here is the location so we can be on the same page. You re right though, the AC will not come on when the car thinks it is 44 degrees outside. You need to remove the right front headlight. Check out the image below.

Jul 14, 2026 at 7:56 PM
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LAVELL11
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Ok thanks i will look into it once I get free time
Jul 14, 2026 at 8:08 PM
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STRAILER
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You are welcome.
Jul 15, 2026 at 4:31 PM
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LAVELL11
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So I decided I'm going to just replace the compressor. I ran live data on my ambient air sensor it was reading correctly 91 degrees on the scan but on my dash it said 44 degrees. It's hot today so I made sure it was right thur my phone to verify. On the scan tool it's accurate but on the dash it's not compressor still ain't turn on so replacement coming
Jul 15, 2026 at 9:08 PM
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STRAILER
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Okay, that sounds good, it can be the display that is messed up if the scanner is telling you the temperature is correct. Any other codes in the system?
Jul 15, 2026 at 11:16 PM
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LAVELL11
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Ain't no other code on that's the crazy part
Jul 15, 2026 at 11:30 PM
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LAVELL11
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I can look into that display at a local junkyard too find a good used one
Jul 15, 2026 at 11:31 PM
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STRAILER
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Yep, that will work, I would check ebay as well, I have had good luck with parts from there.
Jul 16, 2026 at 1:25 PM
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LAVELL11
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Ok thanks
Jul 16, 2026 at 2:26 PM
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