AC not blowing cold but Gauge pegs into red area indicating there's freeon in sys.

[Sprung Monkey]

05 Chevy Express 3500.
AC not blowing cold but Gauge pegs into red area indicating there's freeon in sys.
my AC was working fine 2 summers ago last year not so much an now it's worst.blowing barley cool.
I connected the el cheapo single gauge started engine gauge moved to the red, then compressor kicked on gauge went to lwhite for low then back to red.

I stopped bc I didn't want to over charge. or is my sys. way undercharged an I should continue charging?
please advise an thanks

 

[Mooseman]

You need a two gauge setup. The low side will show higher pressure when the compressor is off and then drops. To me, that looks like it's under charged or there is a severe blockage preventing the flow of gas. Maybe the orifice tube is plugged. At idle, it should be running steady and not letting the pressure drop so much that the low pressure switch kicks off. To really know how much refrigerant you should put in, you should have it evacuated and refill with the amount by weight as per the manual or sticker under the hood. And before that, you should check for leaks.

 

[Sprung Monkey]

I think your correct on being low on freeon. since it's low maybe I should crack open the sys. an let out whats in there then remove an inspect the orofice?

at idel I do hear an see the compressor kick on just for a sec. then back off is this why you suspect the blocked up orofice tube.

what I am concerned w/ is overcharging an having the sys. explode in my face.

when i rebuild the whole sys. (so I know what the orofice filter is)on my car I had the 2gauge an rented the evac pump. mite be time to get another 2gauge set. you know I paid $30. for the single gauge at autozone an the inexpensive 2gauge is the same price. thanks Mooseman

 

[TJBaker57]

FWIW, those that have an OBD2 adapter and an app that reads live data PIDs.... You may be able to read the high side pressure with a custom PID entry. It very likely will not be included with the app but creating a custom PID entry can often be added.

I know my TrailBlazer 4.2 PCM broadcasts this data near continuously.

 

[Sprung Monkey]

this switch has been known to leak
GM Genuine Parts 15-5715 (01132749) Air Conditioning Cycling Switch

since there's not much freeon maybe half a 12oz can maybe I can get away w/ loosen a service valve to empty the remaining freeon then swap these service valves?

this low preasure valve has been known to leak.

this high preasure valve has been known to leak

high preasure plug.

and orofic filter

then rent the vacum an buy some decent dual gauges? add some freeon w/ the dye to check for leaks. I probaly should pump in shop air w/ dye.but would prefer to just bolt on a few known to fail parts an hope thats the only leak.

 

[Sprung Monkey]

FWIW, those that have an OBD2 adapter and an app that reads live data PIDs.... You may be able to read the high side pressure with a custom PID entry. It very likely will not be included with the app but creating a custom PID entry can often be added.

I know my TrailBlazer 4.2 PCM broadcasts this data near continuously.

I'd should have this OBD2 scanner an related probaly torque pro app. just haven't pulled the trigger on it yet. now I do have this scanner an I believe it reads live data.

https://www.amazon.com/dp/B07Z3HB7DR/?tag=gmtnation-20

thanks

TJBaker57​

 

[Mooseman]

To know where you are losing refrigerant, you could get yourself a leak detector before you open up the system and start throwing parts at it.

Amazon.com : refrigerant leak detector

Doesn't have to be expensive. I've had one from HF for years and has been very useful in finding leaks for me.

https://www.harborfreight.com/electronic-freon-and-halogen-leak-detector-92514.html

Since it still has some gas left, it may be just a small leak but better to check.

I doubt scanner could show A/C sensor data. Looks pretty basic. Best would be a dongle like this one and @TJBaker57 could show you how to add the PIDs on your Android phone or tablet to get that data. A much more useful tool.

https://www.amazon.com/dp/B011NSX27A/?tag=gmtnation-20