Atlas

Hard to say what the issue might be. Anything from the ability to cool the AC condenser up front, to blend door issues in the HVAC unit, to refrigerant charge, to compressor issues or issues in the lines. Report back what the techs find on the 29th. GM has service publications which list acceptable vent temperatures and AC pressures at given ambient temps and humidity. They probably won't touch the system if it's operating within those ranges. I'm also surprised to hear your 2024 with the L8T is still using R134a? I was pretty sure the HD's had switched to the new refrigerant around 2020.

tldr; Shade tree mechanic stumped by variable displacement AC compressor. Not Silverado related, but for my 2000 Camaro SS. I've never really used the AC since acquiring the car a good handful of years ago. I plan to take it on a trip this summer so I wanted to make sure the AC was in good shape. On an 73 degree day in the shop with the car idling I set the AC on "Max", temp set to cold, and fan on hi. The compressor turned on and air turned nice and cold. I let it run for several minutes but noticed the compressor never cycled off. The engine was up to temperature enough that it began cycling the cooling fans on high. I had a set of manifold gauges hooked up and it was consistently at about 25 psi on the low side and between 200 and 225 psi (warm engine) on the high side. Per temperature charts, the low side is low (should be 30-35) and the high side is a little high (up to 170 per chart). I read the low pressure as potentially being under-charged underscored by a continually running compressor This was also underscored by temp readings of mid-20 degrees at the vents. Not just cold, freezing cold. Switching off the AC but leaving the HVAC fan on high produced a deluge of condensation underneath the vehicle. I was getting ice buildup on the evap core most likely. The low reading (25psi) concerned me that the compressor wasn't switching off so I swapped out the pressure switch. No change in behavior, still ran constantly. The AC clutch works fine as it engages/disengages with the HVAC switch on command. The compressor relay is good as I swapped it with two different known good relays just to be sure. Having eliminated that, and the pressure switch, I added refrigerant, thinking the constant run and low "low" pressure were signs of a slight undercharge. Makes sense, the car is 26 years old and it doesn't appear the AC system has ever been touched. Adding some R134a didn't meaningfully change the low side pressure. And that's when a lightbulb flashed upstairs. While I consider the car "old", it's possibly "new" enough to have a variable displacement compressor. Did some reading and sure enough. Dangit. I don't work on these for this reason. Adding refrigerant means the compressor will just compensate and won't really change pressures until it's severely overcharged or undercharged. But at least I wasn't getting ice/frost anymore, but instead high 30 degree temps out of the vents. That's more normal, but with variable displacement now I have no idea where my charge level is at. It's probably overcharged now. The high side even with the engine radiating serious heat was never really over about 225. The static pressure at room temperature is dead on, before and after the charge. Both high/low equalize after some rest. I'm thinking I'll need to take it to a shop. I want the proper charge level so I'm not working the compressor too hard. The only way to get an accurate charge is to evacuate and then re-charge with the exact amount specified for the system -- at least that's what I'm reading. Anyone here with modern automotive AC knowledge?

I prefer new, but not without a deal. Historically I've bought severely aged new inventory, leftover model year, unpopular configuration kind of stuff that sits around on dealer lots until they just want it gone. $10k off MSRP kind of stuff on a mid-priced truck. That really, really helps knock down that first year depreciation. It also requires being somewhat flexible on colors and options. I wouldn't buy a 4 cylinder if I was looking for an 8 cylinder, but if I got blue paint instead of black, or a great deal was lacking a minor option, I'm willing to overlook those things for savings. Used <> used. Condition and history are everything. If I'm buying used I'm looking for cream of the crop. The truck from the guy who religiously pampers it, and then decides a year later he wants newer and nicer. NOT the ex-rental vehicle, or the crew cab traded in by the family with 7 kids who like to throw food, and the oil only got changed when there was time long after the oil life monitor started alerting.

@Grumpy Bear the conclusion from your post about doubling engine life has me curious. Are we literally talking an expected life of 250,000 miles potentially becomes 500,000 miles with a step up in filtration for fresh oil at "the oil factory" when it's bottled? I know you said that's a single variable among many, but, that's significant if the implication extends that far into a real world use case. I would think the oil marketing folks would really eat that up and make it known. Particles introduced during oil change is a fairly easy one to avoid, but probably not intuitive as one would think. I.e. using a clean funnel. But...what was it wiped with? Paper towel leaves behind little fibers. A solvent if not dried is not something one would want to introduce into their engine with clean oil. And, keeping the oil filler neck clean and free of buildup.. Look at some guys engine bays and they're an absolute mess. Some say that's better than the drawbacks of cleaning it. I'm not a buyer of that idea. I've also wondered if "flooding" the top end of the engine with oil while filling is a bad idea. During normal lubrication the oil flows in a gutter back into the galleys. But if you flood the area you're potentially washing the top of the rockers, springs, and other areas which may not get much oil wash normally, and you're mixing all that into the new oil. I just don't have the patience to pour slowly.

I'm guessing moving the headlight switch to virtual was for cost savings. The headlights are already controlled via the canbus so why not eliminate the need to manufacture a switch and take up real estate. I prefer a physical switch but I also realize I don't actually use it 99% of the time. The 1% of the time I do want it, I'm guessing it's a pain to turn the lights on. Probably 1-2 screens deep in the infotainment just like in the newer Colorados.

On the subject of OLM, Gm's OLM tool may be more "informed" than others brands. I recall OLM's in mid-2000's Chrysler products literally counting down a set number of miles. That's all the OLM appeared to be. I would actually expect GM to be able to explain the parameters that their OLM takes into account from a high level. No, I would not expect them to disclose their software coding or data analysis around their parameters. So we're talking about two different topics, so to continue the subject on the other one, I'd be curious to know how much "standard particulate matter" in fresh oil is able to be filtered at first start by a fresh oil filter. How much particulate matter is enough to "matter"? I.e. how much of a "lever" do we think this equates to (variability in particulate content, in fresh oils, between different makes/brands, some which filter less, and some that filter more). We can say that more particles = more wear = shorter engine life as a logical statement and use that data with a little marketing to scare people into selecting a more refined/filtered oil. Using a similie, is this like deciding to forego two alcoholic drinks in a lifetime because we're worried about the potential impact on lifespan? Are there numbers which translate the ISO test results into a quantifiable increase in wear for a given engine/use case?

Coming back to this question, *my* answer is no, it's not something about which I'm knowledgeable. I'd need to read up on it and understand how it applies to we the consumer and our oil change regimens. One of your bolded points is that fresh oil in a container contains particulate matter. I don't think I'm surprised, maybe a little bit that it seems to be a major factor, but there's manufacturing process involved in oil and it doesn't exactly come in sterile packaging. How much is filtered out on the first start by an acceptable quality filter (AC Delco, as a baseline) filter? On the GM OLM discussion, just saying that the "number of engine revolutions" appears to be a factor in oil life... cough... maybe driving style *does* matter.

$5.40 for 87 this morning, still pretty high. We all gotta pay for that $300 Billion gift to Iran somehow.

I'd be OK if SLT disappeared. Mind hits the gutter same as when I see TRD plastered on the side of a Toyota. TRD SLT

So you're saying Texas' red leadership can't even control crime in your undeniably "red" state. Got it. Crime in populated areas kind of makes sense. Criminals need to go where the money and people are. That's another reason gas prices are high in desirable places.

Our state has a lower violent crime rate than Texas and where I live it's virtually nothing. But, do you, cucumber. Keep that blindfold on regarding your state's own corruption.

Knut, Texas isn't really considered to be part of the Midwest.

I always thought "Silverado LT Z71 Trail Boss" amounted to word salad, as well as "Custom Trail Boss". LT didn't really mean much since the disappearance of LS trim, and Z71 doesn't mean much either. I bought my TB for the appearance. The name is kind of goofy to me anyway. The trucks are more of a Mall Boss if I'm being honest. Naming conventions aside, I think the lineup is good for '27.

There's a reason, many reasons, actually, some of us won't live in the Midwest. The higher price of fuel out here on the West Coast is absolutely worth it. And I did live in the Midwest once. No thanks!

I like it. In a world of vehicle front ends that look like they've had a little too much nipping and tucking, I appreciate that GM went with a bold and professional look for the new Silverado and kept the aggression understated. The new 1500 looks a little more like the current 2500. The interior looks well done as usual, although I'm not a fan of billboard screens on the dash. At least recess the gauge cluster screen. I see passenger screens as "keeping up with the Joneses'" in automotive interiors of late, which is fine. I don't think they belong in most pickups, but choice is good. Maybe some day I'll appreciate having one. Probably not, but, maybe. Yet another steering wheel and airbag design. I wonder what it costs to have so many different models of airbags and buttons and steering wheel frames. IMO, pick a good one and stick with it. The new one is very...luxurious...looking. Again, not bad, but also not what I'd expect in a pickup. GM has left us awaiting engine choice announcements and official details. What will I be ordering on day one? Nothing. I like my 2025 and it would be silly to get rid of it just to have a 2027.

Portland

The spot price of crude is still around $83/bbl. That's near-term delivery. Historically, that's translated to ~$3.50 national average per gallon. Still high. WTI futures are are just over $75

Do you have knowledge of the complete agreement? Was it sent to everyone with TCSS? I think you might be unaware that "Space Force" existed within every military branch before the branding/merch effort of calling it out as a separate force. So there wasn't a weapon, we don't have the uranium, and we've messed up Middle Eastern oil infrastructure so we can enjoy high gas prices for ...how long? Make it make sense.

Or is it the people with TCSS are the only ones who think there's something useful here? I mean, the Strait was open before the war, gas prices were high but almost reasonable, and there was an entire deal which allowed global oversight of any Iranian nuclear program. Today, we still don't have their "stockpile" of uranium, there was no nuke found. I'm trying to reason with you here bud, but it kind of seems like the whole thing was a big distraction or boondoggle for profits. Because your last line kinda makes it sound like it finally penetrated the slab of granite between your ears that they probably didn't have a weapon.

Being told 38 times for sure a deal is imminent and me not putting a lot of faith in that outcome after the 3rd or 4th time means I'm not a cucumber. But you are welcome to do you, as you are. What's with your Steph Miller emojis, anyway? Why are you crying?

That's kind of how I bought my current truck, not on an oil change, but on a service visit. My Camaro was having recall work performed. Walked over to the sales department with a steak tied around my neck and the rest is history. No, I didn't sell the Camaro. Yes, I was already looking for a truck. They wanted to move my mid-optioned LT to make room for '26's. It had been on the lot for ~100 days already. It was an unpopular config for the loan and lease buyers. The sales department was thrilled to have someone, anyone, interested in buying something. As for dealer service, I worked for a car dealer as a kid. Wouldn't ever take my car to a dealer to have the oil changed. Just as you can get decent service and work, you can also get really sloppy work. Oil change techs are usually young ones who just learned how to turn a wrench. It doesn't pay well. It's high volume production work, move cars through as fast as possible. As the saying goes, if you want it done right, do it yourself. So I do just that.

Gas dropped a whopping $0.03 to $5.46 for regular this morning. I wonder why the deal isn't a deal. It's a concept of a deal to occur sometime over the next 60 days. So far Iran says the Strait will not be "free", and still no nuclear concessions have been agreed to. So basically we begged them to relent in exchange for cash, with a likelihood we'll give away the farm in said "deal". Market Manipulation Monday? Taco Tuesday is always the next day.

Just a guess based on the mentions I've seen on this forum... Failing coolant control valves (LM2, LZ0) No start / long crank issues (LM2) Thrust bearing failures (LZ0) Timing chain failures (LM2) Fingers crossed GM has more revisions and updates in the work because the 3.0 is awesome (when it can be trusted).