1999 Chevy Blazer - No AC Issue

[Capt. Mike]

Looking for a little guidance on what my problem could be with this vehicle.
The vehicle has been sitting for quite some time, other than a 10-15 minute start & drive every couple of months. I recently started the vehicle on a 90+/- degree day. After 15 minutes of driving around, switching back and forth between the AC and MAX AC settings, I could not get any cold air production.
I parked the vehicle & checked under the hood, the compressor was not running. I attached a can of 134a to get a pressure reading - which was -0-. Thinking that maybe the system was low, I began adding gas. Once the pressure reading reached 30, the compressor began cycling on/off in approximately 20 second intervals - but still no cold air. Each time the compressor would kick on, the pressure would jump to 50-60. So I do not believe that the issue is refrigerant related or compressor related.
Any suggestions on where to start my search for the problem?

[Tom Greenleaf]

If your zero pressure was even with a warm engine after being cold you have a huge leak. What pressure just for now did you read 50-60, high or did low go up somehow with compressor on?

Are you using a can with a gauge on it? Stop now if so, wrong totally.

If sure zero again now after it had some you might hear this leak, engine off. Would help to find it either way before you try to fix it while you can detect where it is the most ways.

That's just the beginning at least know what's ahead.

Note: Any system if at true zero has sucked in air you have to start from a well held vacuum which it could but before that try to find where it's leaking out.

IDK - guess low use vehicle, now about 20 and probably the doomed RV4 compressor not the first one the shaft seal would take a hit. May not show oily evidence if low enough and leaked while off might not show there but is or anywhere refrigerant travels.

Both pressures please is has both fittings. If a can with gauge and absolutely sure nothing but 134a refrigerant is in it use a couple ounces just for a quick test with it. If it claims any other features of the product we call those "Death Kits" for a reason! Beware,

[Capt. Mike]

Yes, I was using a can with a gauge. Mainly because it was the only thing I had on-hand!
Looks like I'll have to invest in a set of gauges. And yes, the factory-installed system has both fittings. So I'll try this and report back after.
When I added the gas and the gauge rose to around 30, it caused the compressor to kick on. With the compressor on, the pressure rose to 50-60.
With the engine off, I could not hear any leaks nor could I see any oily discharge from the hoses, compressor or condenser.
Thanks for the advice. It may be a week or two before I can follow-up.

[Tom Greenleaf]

Low side would DROP pressure with compressor engaged. If you aren't sure of when it's engaged or at idle just looking at compressor's clutch this trade not just a hit and run quick fix isn't going to work and make this all worse. Here to help and site is on purpose free to use for you.

This is a trade of it's own takes mega thousand$ in equipment and tons of experience even after any specialized training. It's physics, and algorithms of know how 3 dimensions all at once if everything was perfect. Temperature, pressures and knowing what state the refrigerant is in and where. That and 10,ooo other observations all at once or a machine that just counts what comes out and counts what you tell it to put back it and will quit if anything isn't right and tell you what it noticed.

Just now back from Home Depot as an example reading a Death Can and gauge quickly. I had things to do. Just to notice the color gage on can and cheap junk single hose was a 50PSI range that said you are all fine if needle point here, too low it there and too high if in another spot. Low - yellow, green is all wonderful, red a warning in 50 PSI increments. No time there to read 3 different languages if it contained any sealers or oil it couldn't know what belongs in your vehicle! No sealers anyway - never! You need the # on the mark and that doesn't tell you it's correct yet just you are in range of OK with given temps, pressures and RPM of the engine add in the air flow noticed thru the grille is the great clue. Even that doesn't tell you it's exact but a mandatory diagnosis tool if not right to move on from that.
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OK. Gauges that can be trusted I would still compare with a set that you are sure of! You can rent them for free for a 100% deposit on hold for safe return at many parts outlets along with vacuum pumps and some things for A/C. Borrower beware of accuracy or if the things are contaminated.

The most important thing is know when to quit and get help. Mistakes are so dang costly makes the paid help look cheap. One time fixes about can't cover the costs of the equipment needed not even counting any labor charges.

Try again to find the leak but want you to read the whole can it's not right! Pressure can't go up with compressor on unless already wildly wrong somehow to be found. You could look for leaks if just looking for oil evidence that couldn't be there on parts from anything else. Behind clutch, lines anywhere especially connections. The condenser up front it a spot showing oil suspect. Drain for condensate that allow water out from the evaporator with a Q-Tip should come out dry maybe dusty no oil. Should be a rubber neck may or may not be floppy ended so air doesn't go back in in this if so can just cut that off a little fit something inside for inspection.

Good luck. There are things you can do just please don't believe the exact thing I just looked at blasting all over the display anyone can do this in minutes is wild total bullsh*t and dangerous. No clue how they are allowed to lie like that on packaging and displays????????

Please ask if I've confused you with anything. No motivation to do anything but help you or warn you where problems happen and how to deal with them starts with informed information from you,

[Cornbinder89]

Pressure rise with the compressor on and a gauge on the low side means there is a restriction between the low side tap and compressor. Unless you have some refrigeration experience, I think this a time to STOP and seek some professional advice. The rise indicates there is more of a problem than just a leak, which is a big problem in itself.
From what you are reporting, the system is going to need some internal work. Leaks are bad enough to deal with and hard to find without "sniffers" and a good bit of luck. Internal problems like you are reporting, require a good understanding of the dynamics of the system so the clues will point you in the right direction. All this assumes the tools you are using for diagnostics are good and accurate and you are reading them in "real time" so you know what is happening when.
I am not trying to hold "trade secrets", but in reality there is so much you need to know and understand to the point that you can "see" into the system with your mind, by what the actions of the gauges, compressor clutch and condenser and evaporator temps are telling you.
It is not going to be a simple, top it up and all is fine thing.
An air conditioning compressor can easily exceed 450 psi and liquid refrigerant can BLIND you permanently, this is nothing to fool around with. I've been around a few hose bursts in my time, and lucky no one got hurt.
Hooking things up wrong can pump pressure back into the can and it can explode in your hand!

[Tom Greenleaf]

So well said Cornbinder89: I was caught up a lot with how thinking more like the hose to kit-can junk might be collapsing or something part reading pressure from can's pressure really destroy using those for diagnosis,