Ambient Temp Sensor?

Are you talking about the air temperature sensor for the engine or HVAC? IF it is for the engine the sensor is integrated into the MAF sensor. There is no air temperature sensor for the HVAC system, what problem are you having?

Thank you for your response. I am talking about the HVAC one. I have a Scangauge III attached, and one of the metrics it reads while driving is ambient air temp. Lately, it has been reading very high numbers like 150° ect. Its certainly not that temp outside. When it reads that, the AC will shut off intermittently, usually while traveling through the desert on a hot day. I'm figuring the AC is turning off to save the engine from overheating because it thinks its hotter outside than it actually is. I purchased part #25775833 (ambient air temp sensor) to swap it out to hopefully show the correct temp on the gauge, and to allow the AC to work when I need it to.

Can we double check the year, make model engine size, I am noy showing an ambient air temperature sensor for the HVAC system.

2006 Chevrolet Express 3500 6.6 Diesel

Yep, there is no ambient air temperature sensor for the HVAC system for this vehicle.

Thank you for the clarification. I am left with the following questions-

1. Why does rockauto / autozone list that part as fitting?

2. Where is the ambient temp sensor?

3. Is the IAT sensor incorporated into the MAF like you said? The MAF has 5 wires going to it...

4. Does the vehicle take the IAT reading and use that as the ambient temp as well?

5. All things considered, why would the A/C intermittently blow hot only during long highway trips across the desert?

Thank you for lending your expertise.

That type was used on some of the versions depending on the options. A quick way to tell would be to look for option DF5 on the RPO sheet in the glove box. If it has it they were in the top front center of the core support near the latch. So there are some out there that use that part (Believe it's on the conversion or HD units like cab/chassis for ambulance and such)
The Intake air Temp Sensor is part of the MAF sensor in the intake path, it's a tiny thermistor that sets next to the hot wire. That is why there are 5 wires. Pins 2 and 4 are the IAT One side is grounded and the signal changes based on the temp of the air passing by.
BUT GM played a trick on the diesels and uses 2 intake temp sensors. It uses the signal from sensor two for the HVAC as well as to compare to the IAT in the MAF. It's in the intake manifold below the air intake duct on the top of the engine. They usually stick in place pretty well. That is it in the last image. FYI, the changing readings are commonly corrosion in the connector itself. It's on top in the harness. Hope that helps.
OOPs, missed the last part. Long trips with the A/C working hard can cause the moisture in the air to condense and block the core with ice, the unit shuts off, the ice melts, it comes back on now that there is airflow. Easy way to tell if that is the reason. When it stops, let the vehicle set for about 10-15 minutes with the engine idling and then look under it, got a big puddle of water under the drain? it's icing up.

Thank you for taking the time for that detailed response.

Ok, I do not have the DF5 RPO code, so I will stop looking and return that new ambient air temp sensor.

Also, do you suggest cleaning the connector and / or replacing the IAT2 sensor? (There are no codes or CEL).

My main issue that I am trying to remedy is the A/C blowing hot sometimes. I never thought about it icing up, but there has definately been a puddle of water under when I park. How do I prevent the icing up? Would putting it on fresh air instead of recirculate when the A/C is on help any? Are there any other tips or tricks?

Freeze up is a hard thing to deal with at times. In a dry desert it could help to pull in the dry air. My general method is to run on recirculate until it's cooled down. Then switch once it's cold to let the core thaw out. I have also had times where I would leave the AC running and select heat to dry the core. Comes down to what works for you based on the local weather. A lot of the moisture in the system on recirculate comes from the humans inside the vehicle. Add a cup of coffee or other beverage and you get more moisture. The core normally runs cold and it has a lot of surface but very small passages so even small amounts of moisture can cause issues.

Ok, I will givr those a try the next time I am on a long trip, thanl you.

Please let us know, I am interested to see what happens.