I can't say for sure about the GM truck, but I've owned a couple of vehicles that have compressor speed sensors on the A/C. Our Lexus A/C stops working every time we go through a puddle of water with any speed. So spraying sensors while idling probably won't duplicate what happen when water splashes on the compressor or belt at 1300 RPM or more. I never feel anything slipping or hear a squeal (not likely with serpentine belts, anyway), but it seems like the rush of water may try to "stall" the compressor for a split second. Since the sensor is very sensitive, it disengages the A/C clutch which will not re-engage without driver input. We don't usually notice it until the car starts warming up. But, simply pressing the "auto" button turns it back on. I have never tried to diagnose the exact issue since we aren't driving in heavy rain that often. Here's what Google AI came up with:
Yes, a faulty A/C belt speed sensor can cause the air conditioning to stop working in a GM truck. While the term "belt speed sensor" is less common, the vehicle's computer uses a related sensor, such as the A/C compressor speed sensor, to monitor the A/C clutch and serpentine belt. If this sensor fails, the engine control unit (ECU) may disable the A/C system to prevent further damage.
How a faulty speed sensor affects the A/C
In modern GM trucks, a sensor on the A/C compressor monitors its rotational speed. The vehicle's computer uses this information as a safeguard.

• Safety mechanism: The system will disengage the A/C compressor clutch if it detects a difference between the engine speed and the compressor's speed. This prevents the clutch or belt from being damaged if the compressor locks up or the belt is slipping.
• False-positive shutdown: If the sensor itself is faulty, it may send an incorrect signal to the ECU. This will cause the ECU to disengage the clutch and shut down the A/C system, even if there is no physical problem with the compressor or belt.

 

Yeah, there's nothing fancy like speed sensors in a 2007. Assuming you don't have pressure gauges (borrow a set?), put a scan tool on it, and monitor the pressure. Listen / watch for the clutch engaging.

Report back findings.

If the belt was slipping THAT much, you'd hear it howling like crazy. You'd loose brakes and power steering... enough that you'd notice.

 

While the issue could be with a connector that isn't making a great connection, I would think it is more likely as dr.fiero stated that checking the A/C refrigerant pressure would be a good thing to do. What I suspect is that you are low on refrigerant and the rain is cooling the condenser more than without any rain and the cooler you can get the high pressure side (condenser) the lower its pressure will be and the low pressure switch is turning off the compressor.

 

Yup, and then you hit that threshold of enough pressure to allow it to turn on, which causes the low pressure side to drop, and it falls under the turn on point, which turns it off... which lets the pressure rise.... and around and around you go!

 

BTW, you should not (NEVER) be troubleshooting this issue or any similar issues by spraying water on the wiring harness, its connections, especially near any of the computer modules and its connectors.

 

I did check pressures already (it was actually the first thing I checked and they are good), sorry i didn't put that in my original post. I didn't think that would be an issue since the AC works good at all other times. the belt does not make any noise what so ever, however, i do not know how old it is, so it could stand to be replaced as it is started to get warn. I bought the truck from my brother in law and he is not sure what the mileage was at when he replaced the belt.

here is an example of the AC turning off: I drive to my father in laws every couple of weekends and it is a 2-1/2hr drive 1 way. I end up driving thru a rain shower within the first 20mins of the drive and the AC turns off and the snowflake flashes on the climate control anytime I try to turn the AC back on, so I give up and crack the windows a little bit, the rain has stopped, the road is no longer wet and i have been driving for another 30-45 mins and all of the sudden the AC just turns back on. it stays working again now until the next rain. it has been doing this since the beginning of spring 2025.

My wife and I drove from Minnesota to Galveston and back in Feb this year, on the way back the truck started popping fuses for the turn signal. I thought it needed a new turn signal switch/cruise control. I replaced it, but still popping fuses. turned out there was a wire from the front passenger turn signal that had started grounding out to the frame. It was almost pinched in the frame as it ran across to connect to the rest of the wire harness. after finding this, I'm kinda paranoid, that's why i brought it up and not sure if it might help.

 

One other thought I had is that there is an ambient air temperature sensor which I believe is located behind the grill and if it is not working correctly and believes the ambient air temp is very cold then that can keep the A/C compressor from running. I don't have a lot of details for your truck though in this regard but it certainly could be that the sensor has a fault in it or perhaps a crack and the rain is causing it to fail. I am not sure about all code readers but those that have real-time readings should be able to determine if this is the case, and if your outside air temp display is reading incorrectly then that would be a clue as well. I will add that the A/C evap itself has a temp sensor but I don't think that there is one for all year models and I am not sure if yours would have one or not. In any case, I now suspect that the ambient air temp sensor could be your issue and they can be tested with an ohm meter, although they are low cost (<$20) so while I don't like to replace parts just to see if that corrects the issue, I don't mind doing that so much when the part is not very expensive. They must go out often as they are widely sold at almost every auto parts stores. ~BB

 

Ill see if i can find it, I do believe i remember reading other posts about a sensor right behind the grill, but i was under the impression it was for the unit inside the cab of the truck (in the mirror) that gave the outside temp, but really had no idea.

I'll let you know what I find out

thanks,

 

Thanks for all the help so far.

I did find the Sensor, but it seems to be working fine which is a good thing, but gets me no closer to a solution to my problem. I'm not sure if this is correct or not though, the AC stayed working with the sensor unplugged. It has GM 15035786 on it and when I looked it up, that is the ambient air temp sensor.

 

I haven't looked deeply into the 2007 models, but I am aware that many similar trucks have 2 or 3 sensors. In addition to this link, I recall some have a sensor at the bottom of the passenger side exterior mirror. These sensors are commonly reported to affect the A/C but I am not sure which sensor is used for the A/C. My understanding for most is that the ambient air temperature sensor sends its data to the ECM and the ECM shares the data to the A/C control module, although and again, I am not sure which sensor that would be but likely the manual I shared earlier may direct you to how many and where they are located. In any case, check this post out as it may add value into your issue. https://www.duramaxforum.com/threads/ambient-temperature-reading-on-mirror.1008127/

 

Also a point to add, in the distance past I had looked into a similar issue but I don't recall if what I remember was verified. With that in mind, my understanding is that some trucks and in particular the base models may not use the ambient air temp sensor and the higher trim models with digital thermostat setting do use the sensor for better climate control and I suspect likely have a different controller for the climate system. Meaning that you may find documents that state the sensor is unrelated to the A/C and others that say otherwise. Yours being a Sierra SLT makes me believe yours does have the premium climate control system that a base (in particular a base Chevrolet) would not have. Also, I seem to recall that the sensor itself is a different (but looks almost identical) depending on the climate control system either being the base or premium control system. Not that this is necessarily all that helpful but imo good to know. ~BB